when 1 mole of reacts with to form according to the following equation, 108 kj of energy are evolved. is this reaction endothermic or exothermic?

Answer:

condensation nuclei

Explanation:

Answer: NA = no of molecules / no of moles

NA = no of molecules × molecular weight /weight

Explanation:

The volume of chlorine gas at 46.0°C and 1.60 atm that is needed to react completely with 5.20 g of sodium to form NaCl is 1.85 L

We'll begin by obtaining the mole of 5.20 g of sodium. Details below:

Mole = mass / molar mass

Mole of Na = 5.20 / 23

Mole of Na = 0.226 mole

Next, we shall determine the mole of chlorine gas needed. Details below:

2Na + Cl₂ -> 2NaCl

From the balanced equation above,

2 moles of Na reacted with 1 mole of Cl₂

Therefore,

0.226 mole of Na will react with = (0.226 × 1) / 2 = 0.113 mole of Cl₂

Finally, we shall determine the volume of chlorine gas, Cl₂ needed. This is shown below:

PV = nRT

1.6 × V = 0.113 × 0.0821 × 319

Divide both sides by 1.6

V = (0.113 × 0.0821 × 319) / 1.6

V = 1.85 L

Thus, the volume of chlorine gas, Cl₂ needed is 1.85 L

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The moles of NaF that must be dissolved in 1.00 liter of a saturated solution of PbF₂ at 25˚C to reduce the [Pb²⁺] to 1 x 10⁻⁶ molar is 2.0 x 10⁻⁵.

The solubility product expression for PbF₂ is given by:

At equilibrium, the product of the ion concentrations must be equal to the solubility product constant. We are given that the [Pb²⁺] in the saturated solution is 1 x 10⁻⁶ M. Therefore, we can use the Ksp expression to calculate the concentration of F- in the solution:

Now, we can calculate the amount of NaF needed to reduce the [F⁻] concentration to 2.0 x 10⁻¹ M. Since NaF is a 1:1 electrolyte, the concentration of F- will be equal to the concentration of NaF added.

However, we need to dissolve this amount of NaF in a saturated solution of PbF₂. Therefore, we need to check that the amount of NaF we added will not exceed the maximum amount that can dissolve in the solution at 25˚C.

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The hammer and the feather are dropped from  same height by the astronaut on the planet without the air. The feather will fell at the same rate as the the hammer.

The hammer and the feather are dropped from equal  height by the astronaut on the planet without the air. They were the essentially in the vacuum, and there was the no air resistance and because of the feather will fell at the same rate as compared to the hammer, the Galileo had to concluded that the hundreds of the years before.

All the objects that released together will fall at the same rate excluding the factor of the mass.

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The amount of excess reagent that will remain would be 11.76 g.

To determine the excess reagent in the reaction, we need to first determine which reactant is limiting and which reactant is in excess.

The balanced chemical equation for the reaction is:

6Na + Fe2O3 -> 3Na2O + 2Fe

The molar mass of Na is 23 g/mol, and the molar mass of Fe2O3 is 159.69 g/mol (2 x 55.85 g/mol for Fe + 3 x 16 g/mol for O).

Using the given masses, we can calculate the number of moles of each reactant:

According to the balanced chemical equation, 6 moles of Na react with 1 mole of Fe2O3. Therefore, the number of moles of Na required to react with 1.57 mol of Fe2O3 is:

(1.57 mol Fe2O3) x (6 mol Na/1 mol Fe2O3) = 9.42 mol Na

Since we only have 8.70 mol of Na available, it is the limiting reagent. This means that Fe2O3 is in excess.

To determine the amount of excess Fe2O3, we need to calculate how much Fe2O3 is required to react with 8.70 mol of Na:

(8.70 mol Na) x (1 mol Fe2O3/6 mol Na) x (159.69 g/mol Fe2O3) = 238.24 g Fe2O3

Since we only have 250 g of Fe2O3, the amount of excess Fe2O3 is:

250 g - 238.24 g = 11.76 g

Therefore, the amount of excess Fe2O3 left after the reaction is 11.76 g.

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The outcomes to the scan had been now not all similar. The pots with the pH of 5.0 had no growth whatsoever. The pots with the pH of 6.0 had little growth, each with only four blades of grass. The pots with a pH of 7.0 grew well, one pot with extra blades of grass than the other, an average of 11 blades of grass

Natural soil pH depends on the rock from which the soil was once fashioned (parent material) and the weathering procedures that acted on it—for instance climate, vegetation, topography and time. These approaches have a tendency to purpose a decreasing of pH (increase in acidity) over time.

There is disruption of nutrient absorption by way of the plants if it's pH increases, and hence, soil fertility is reduced, alkaline soil's pH does not lead to make bigger in nutrient absorption, soil illness does not happen.

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There are 7.52 x 10^22 molecules of carbon dioxide gas, CO2, in 0.125 moles.

        The number of molecules in a given number of moles can be calculated using Avogadro’s number, which is approximately 6.022 x 10^23. This number represents the number of particles (atoms or molecules) in one mole of a substance.

         To calculate the number of molecules in 0.125 moles of CO2, we can multiply the number of moles by Avogadro’s number: 0.125 moles x (6.022 x 10^23 molecules/mole) = 7.52 x 10^22 molecules.

         Avogadro’s number is a fundamental constant in chemistry and is used in many calculations involving moles and molar mass.  

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the overlap integral simplifies to:

S = c1c2 + d1d2d1d2.

To calculate the overlap integral between two linear combinations of atomic orbitals on a carbon atom in ethene, we first need to express the orbitals in terms of the hydrogen-like atomic orbitals. Let's assume that the two orbitals are denoted as ψ1 and ψ2, and can be expressed as linear combinations of the hydrogen-like atomic orbitals ϕ1 and ϕ2 as follows:

ψ1 = c1ϕ1 + d1ϕ2
ψ2 = c2ϕ1 + d2ϕ2

where c1, d1, c2, and d2 are constants.

The overlap integral between these two orbitals can be calculated using the following formula:

S = ∫ψ1ψ2*dτ

where dτ represents the infinitesimal volume element.

Substituting for ψ1 and ψ2, we get:

S = ∫(c1ϕ1 + d1ϕ2)(c2ϕ1 + d2ϕ2)*dτ

Expanding the product, we get:

S = c1c2∫ϕ1ϕ1*dτ + c1d2∫ϕ1ϕ2*dτ + d1c2∫ϕ2ϕ1*dτ + d1d2∫ϕ2ϕ2*dτ

Since the hydrogen-like atomic orbitals are orthonormal, the integral of ϕ1ϕ2 and ϕ2ϕ1 will be zero. Therefore, we can simplify the expression as follows:

S = c1c2∫ϕ1ϕ1*dτ + d1d2∫ϕ2ϕ2*dτ

Using the orthonormality of the hydrogen-like atomic orbitals, we know that the integral of ϕ1ϕ1 and ϕ2ϕ2 will both be equal to 1. Therefore, the overlap integral simplifies to:

S = c1c2 + d1d2d1d2.

In order to calculate the value of S, we need to know the values of the constants c1, d1, c2, and d2. These constants will depend on the specific linear combinations of atomic orbitals that we are considering. Without this information, we cannot calculate the value of the overlap integral.

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If two orbitals as linear combinations of two atomic orbitals on carbon atom in ethene, then value of the overlap integral [tex]S_{12} = \int{\phi_{1}}^{*}\phi_{2}d \tau[/tex], is equals to zero. So, option(b) is correct.

Orthonormal atomic orbitals are follow the following property:

Now, we have provide that two orbitals are as a linear combinations of two atomic orbitals on carbon atom in ethene. [tex]\phi_{1 } = \frac{1}{ \sqrt{2} } ( {\psi_{2s }} + {\psi_{2p }}_{2})[/tex]

[tex]\phi_{2 } = \frac{1}{ \sqrt{2} } ( \psi_{2 s} - {\psi_{2p} }_{2})[/tex]

In the ethylene molecule, consists each carbon atom is bonded to two hydrogen atoms. Therefore, for the C-H, σ bond (sp²(C) - 1s(H)) in ethylene, the two sp² hybrid orbitals overlap with the 1s orbitals of the two hydrogen atoms. Let the hydrogen-like atomic orbitals, [tex]\psi_{2 s} and {\psi_{2p} }_{2}[/tex] are orthonormal to each other. So, the overlap integral [tex]S_{12} = \int{ \phi_{1}}^{*}\phi_{2}d \tau[/tex]

[tex] = \int \frac{1}{\sqrt{2}}( \psi_{2s} + {\psi_{2p} }_{2}) \frac{1}{\sqrt{2}}( \psi_{2s} - {\psi_{2p} }_{2})d \tau\\ [/tex]

[tex] = \frac{1}{\sqrt{2}}( \int \psi_{2s}\psi_{2s} d \tau + \int {\psi_{2p} }_{2}\psi_{2s} d \tau - \int \psi_{2s} {\psi_{2p}}_{2} d \tau - \int {\psi_{2p} }_{2} {\psi_{2p} }_{2} d \tau) \\ [/tex].

Using above formula, [tex]\psi_{2 s} [/tex] and [tex]{\psi_{2p} }_{2}[/tex] are orthonormal so, [tex]\int \psi_{2 s} {\psi_{2p} }_{2} d\tau = 0[/tex]. Also [tex]\psi_{2 s} [/tex] and [tex]\psi_{2 s}[/tex] are normalised so [tex]\int \psi_{2 s} \psi_{2 s} d\tau = 1[/tex]. Similarly [tex]\int {\psi_{2p} }_{2} {\psi_{2p} }_{2} d\tau = 1 [/tex].

Substitute all integral values in equation (1),

= 1 + 0 - 0 - 1

= 0

Hence, the required integral value is 0.

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Complete question:

given two orbitals as linear combinations of two atomic orbitals on carbon atom in ethene:

[tex]\phi_{1 } = \frac{1}{ \sqrt{2} } ( {\psi_{2s }} + {\psi_{2p }}_{2})[/tex]

[tex]\phi_{2 } = \frac{1}{ \sqrt{2} } ( \psi_{2 s} - {\psi_{2p} }_{2})[/tex]

where the hydrogen-like atomic orbitals are orthonormal. what is the value of the overlap integral,

[tex] S_{12} = \int \phi_{1} \times \phi_{2}dr[/tex]

a) 1

b) 0

c) 1.5

d) 2

Answer:

Explanation:

The pH of the solution is 10.80

The pH of the solution is 10.80.

Explanation: This can be calculated using the Henderson-Hasselbalch equation, which takes into account the acid dissociation constant (pKa) of the acid and the concentration of the acid and its conjugate base. The HCl dissociates completely in water, so it does not affect the pH calculation.

The methylamine acts as a weak base and reacts with water to form its conjugate acid, which determines the pH of the solution.

The pKb of methylamine is used to calculate its pKa, which is then used in the Henderson-Hasselbalch equation.

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As a result, it is important to store NaOH in a dry and cool place, away from any sources of moisture or water.

NaOH, also known as sodium hydroxide, is a highly hygroscopic solid. This means that it can easily absorb moisture from its surroundings, including the air. When NaOH absorbs water, it can become more corrosive and potentially dangerous.

This is why it is also important to handle NaOH with care and wear appropriate protective gear, such as gloves and goggles. Additionally, any spills or leaks should be cleaned up immediately and properly disposed of according to local regulations.

By following these precautions, NaOH can be safely used in a variety of applications, including in the production of soap, paper, and textiles.

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The pressure of gas is 1.05 atm when a 1.25 g sample of CO₂ is contained in a 750ml flask at 22.5°C.

Molecular weight of CO₂ is 1.25g ,Volume of CO₂ is 750ml,Temperature of CO₂ is 22.5°C and the gas constant is 0.08206 L atm/mol K.

Using the ideal gas law equation the pressure is found to be 1.05 atm.

To calculate the pressure of the gas, we can use the ideal gas law equation: [tex]PV=nRT[/tex]
Where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin.
First, we need to convert the volume to liters by dividing by 1000: 750 ml = 0.75 L.
Next, we need to calculate the number of moles of CO₂ present in the flask. We can use the molecular weight of CO₂ to convert from grams to moles:

[tex]1.25 * (1 /44.01 ) = 0.0284 mol[/tex]
Now we can plug in the values into the ideal gas law equation:

[tex]PV=nRT[/tex]
[tex]P * 0.75 L = 0.0284 mol  * 0.08206 L*atm/mol*K * (22.5 + 273.15) K[/tex]
Simplifying and solving for P, we get:
[tex]P = (0.0284 * 0.08206 * 295.65) / 0.75 = 1.05 atm[/tex]
Therefore, the pressure of the gas in the flask is 1.05 atm.

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The number of moles of bromine trifluoride needed to produce 23.2 L of fluorine gas according to the reaction would be 0.339 moles.

The balanced equation for the reaction is:

BrF3 → Br + 3F2

From the equation, we can see that 1 mole of BrF3 produces 3 moles of F2. Therefore, to calculate the number of moles of BrF3 needed to produce 23.2 L of F2 at 0°C and 1 atm, we need to use the ideal gas law:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.

We can rearrange the ideal gas law to solve for n:

n = PV/RT

At 0°C (273 K) and 1 atm, the value of R is 0.08206 L·atm/mol·K. Substituting the values given, we get:

n = (1 atm) × (23.2 L) / (0.08206 L·atm/mol·K × 273 K)

n = 1.017 mol F2

Since 1 mole of BrF3 produces 3 moles of F2, we need 1/3 as many moles of BrF3:

n(BrF3) = 1.017 mol F2 × (1 mol BrF3 / 3 mol F2)

n(BrF3) = 0.339 mol BrF3

Therefore, 0.339 moles of BrF3 are needed to produce 23.2 L of F2 at 0°C and 1 atm.

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This weather map shows that there is a low pressure system in the north and a high pressure system in the south.

Weather is the study of atmospheric conditions that exist in a specific area over a short period of time. It is the sum of all atmospheric conditions including temperature, humidity, wind, air pressure, cloud cover and precipitation. Weather is an important factor in determining the temperature, humidity and other characteristics of the environment. It affects human activities such as agriculture, transportation and recreation. Weather is dynamic and constantly changing. It is affected by a variety of factors such as solar radiation, air pressure, ocean currents, land topography and human activities. Weather is also affected by climate, which is the average weather pattern over a long period of time. Understanding weather is important for many reasons, including to predict storms and floods, to plan for extreme weather events, and to prepare for natural disasters.

This weather map shows that there is a low pressure system in the north and a high pressure system in the south. The low pressure system is bringing cooler temperatures and precipitation, while the high pressure system is bringing warmer temperatures and clear skies. There is a cold front moving eastward from the north, and a warm front moving eastward from the south.

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when molten CaF2 is electrolyzed by a current of 9.55 A for 19 h, approximately 136 g of calcium metal is produced.

To determine the mass of calcium produced when molten CaF2 is electrolyzed by a current of 9.55 A for 19 h, we'll use Faraday's Law of Electrolysis.

First, calculate the total charge passed through the electrolyte:
Charge (Q) = Current (I) × Time (t)
Q = 9.55 A × (19 h × 3600 s/h) = 653,940 C

Next, determine the number of moles of electrons (n):
n = Q / (Faraday constant F)
n = 653,940 C / (96,485 C/mol) ≈ 6.77 mol

The balanced equation for the electrolysis of CaF2 is:
2F- → F2 + 2e-
Ca2+ + 2e- → Ca

The mole ratio between calcium and electrons is 1:2. So, the number of moles of calcium produced is:
Moles of Ca = 0.5 × Moles of electrons
Moles of Ca = 0.5 × 6.77 mol ≈ 3.39 mol

Finally, calculate the mass of calcium:
Mass of Ca = Moles of Ca × Molar mass of Ca
Mass of Ca = 3.39 mol × 40.08 g/mol ≈ 136 g

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2,3-dimethylbuta-1,3-diene is not a structural isomer of hexyne. Option e is correct.

Structural isomers are molecules with the same chemical formula but different arrangements of atoms. Hexyne is a hydrocarbon with six carbon atoms and one triple bond. Option (e), 2,3-dimethylbuta-1,3-diene, is not a structural isomer of hexyne because it has a different number of carbon atoms and a different type of bond. It has four carbon atoms and two double bonds, whereas hexyne has six carbon atoms and one triple bond.

Options (a), (b), (c), and (d) are all structural isomers of hexyne because they have the same number of carbon atoms and the same type of bond but different arrangements of atoms. Hence, option e is correct.

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Answer:

data given

mass of NaCl 4.56

dissolved volume 20ml(0.02l)

density of solution 1.03g/ml

Required molality

Explanation:

molarity=m/mr×v

where

m is mass

mr molar mass

v is volume

now,

molarity=4.56/58.5×0.02

molarity =3.9

: .molarity is 3.9mol/dm^3

According to molal concentration, the concentration (in molality) of an aqueous solution of NaCl is 0.0047 mole/kg.

Molal concentration is defined as a measure by which concentration of chemical substances present in a solution are determined. It is defined in particular reference to solute concentration in a solution . Most commonly used unit for molal concentration is moles/kg.

The molal concentration depends on change in volume of the solution which is mainly due to thermal expansion. Molal concentration is calculated by the formula, molal concentration=mass/ molar mass ×1/mass of solvent in kg.

In terms of moles, it's formula is given as molal concentration= number of moles /mass of solvent in kg.

Substitution in formula gives the answer but first mass of solution is determined which  is density×volume= 1.03×20=20.6 g , mass of solvent= 20.6-4.56=16.05, thus molal concentration=4.56/58.5×1/16.05=0.0047 moles/kg.

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Ammonia ionizes only partially in water. Option 4 is correct.

When ammonia dissolves in water, it reacts with water to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻), according to the equation: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻. However, this reaction is reversible and only a small fraction of ammonia molecules ionize to form ions. As a result, ammonia is classified as a weak electrolyte, meaning that it only conducts electricity weakly in solution.

Weak electrolytes are characterized by their partial ionization in solution, and they have relatively low electrical conductivity compared to strong electrolytes, which ionize completely in solution. Hence Option 4 is correct.

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The standard enthalpy change for the decomposition of hydrogen peroxide per mole of hydrogen peroxide is -98.2 kJ/mol.

when 1 mole of hydrogen peroxide (H2O2) ( H 2 O 2 ) undergoes decomposition, the heat evolved (ΔH) is −98.2kJ. − 98.2 k J . The molar mass of H2O2 H 2 O 2 is 34.015 g/mol. This means that the mass of 1 mole of H2O2 H 2 O 2 is 34.015 g.

This value is obtained from the standard enthalpy of formation of the products (H2 and O2) and the standard enthalpy of formation of the reactant (H2O2). Enthalpy of formation is the energy change that occurs when a compound is formed from its elements, in their standard states.

The difference between the enthalpies of formation of the products and the reactant is the enthalpy change for the reaction. In this case, the enthalpy change for the decomposition of hydrogen peroxide is -98.2 kJ/mol. This indicates that the decomposition of hydrogen peroxide is an exothermic reaction and it releases 98.2 kJ/mole of energy.

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Energetic molecules such as NADH and ATP are often reactants of exergonic reactions.

Exergonic reactions are those that discharge energy and have a harmful Gibbs-free energy change. In these reactions, the reactants have more free energy than the products, so the excess energy is cast in the state of heat. An exergonic reaction is a chemical reaction where the shift in the free energy is negative.

Energetic molecules like NADH and ATP store energy in their chemical adhesives, which can be emitted in exergonic reactions to drive endergonic responses that need energy input. Therefore, they are usually employed as reactants in exergonic reactions.

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When conducting a crystallization process, it is important to cool the solution at a slow and controlled rate to encourage crystal formation.

An ice bath is preferable over cold water or ice alone because it can maintain a consistent low temperature without causing the solution to freeze solid. Ice alone is too cold and can cause the solution to freeze rapidly, preventing the formation of crystals. Cold water, on the other hand, is not able to maintain a consistent low temperature as the heat from the solution will quickly dissipate into the surrounding water, resulting in a slower cooling rate.

An ice bath, which is a mixture of ice and water, provides a more stable and uniform cooling environment for the solution, allowing for the crystals to form at a slower rate. Additionally, an ice bath can contact the entire portion of the container immersed in the mixture, ensuring that the solution is evenly cooled. Overall, an ice bath is the preferred method for cooling a solution during the process of crystallization.

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complete question is:-

one of the techniques used in this experiment was that of crystallization. when cooling a solution in the process of crystallization, why would an ice bath be preferable over cold water or ice alone? none of the answers shown are correct. ice is too cold and will freeze any solution. cold water would dilute the solution making it impossible for crystals to form. a mixture of ice and water will keep the temperature above freezing and will contact the entire portion of the container immersed in the ice/water mixture.  EXPLAIN.

The rate of the reaction is directly proportional to the stability of the carbocation intermediate, and any changes in the solvent will affect the rate of the reaction.

In an SN1 reaction, the rate-determining step is the formation of a carbocation intermediate. The stability of the carbocation intermediate affects the rate of the reaction.

In this case, if 2-propanol (isopropanol) was used instead of 2-methyl-2-propanol (t-butanol), the rate of the reaction would decrease. This is because the carbocation intermediate formed in 2-propanol is less stable compared to the one formed in t-butanol.

The carbocation intermediate formed in t-butanol is tertiary, which is more stable than the one formed in isopropanol, which is secondary. This means that the reaction will be slower in isopropanol due to the less stable carbocation intermediate.

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False. In a closed system, matter can not enter or exit that is there is no change in the matter of the system.

Three types of systems exist in nature:

1. Open System: In this system, the matter can interact with the surroundings or matter can enter or exit the system from the surrounding. Similarly, the energy of the system also interacts with its surroundings and can be lost or gained.

For example oceans etc.

2. Closed system: In this system, the matter is unable to interact with the surroundings that are matter can't exit or enter the system. While the energy of the system is able to interact with the surroundings.

For example Earth etc

3. Isolated system: In this system, both matter and energy are unable to interact with the surrounding. There is no exchange between matter and the energy of surroundings.

For example thermos-teel bottles etc.

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1) 5.1167 x 10²⁴atoms of chlorine. 2) 248.00 g. 3) 4.8825 x 10⁷ moles of helium. 4) 2.7757 x 10²⁴ atoms of sulfur.  5) Molar mass of Co (cobalt) is 58.93 g/mol.  6) Formula mass =  310.18 g/mol.

Sum of the atomic masses of all the atoms in chemical formula is called formula mass

1.)  Number of atoms = 8.500 moles x 6.022 x 10²³ atoms/mole = 5.1167 x 10²⁴ atoms of chlorine.

2.) Molar mass of oxygen is 16.00 g/mol. Therefore:

Mass of 15.50 moles of oxygen = 15.50 moles x 16.00 g/mol = 248.00 g.

3.) Molar mass of helium is 4.00 g/mol. Therefore, the number of moles of helium in 1.953 x 10⁸ g is:

Number of moles = 1.953 x 10⁸ g / 4.00 g/mol = 4.8825 x 10⁷ moles of helium.

4.) Molar mass of sulfur is 32.06 g/mol. Therefore, the number of moles of sulfur in 147.82 g is:

Number of moles = 147.82 g / 32.06 g/mol = 4.6084 moles of sulfur.

To find the number of atoms, we can use Avogadro's number again:

Number of atoms = 4.6084 moles x 6.022 x 10²³ atoms/mole = 2.7757 x 10²⁴ atoms of sulfur.

5.) Molar mass of Co (cobalt) is 58.93 g/mol.

6.) Ca₃(PO₄)₂ contains 3 calcium atoms, 2 phosphorus atoms, and 8 oxygen atoms.

Atomic masses of these elements are:

Calcium (Ca) = 40.08 g/mol

Phosphorus (P) = 30.97 g/mol

Oxygen (O) = 16.00 g/mol

Therefore, formula mass of Ca₃(PO₄)₂ is:

Formula mass = (3 x 40.08 g/mol) + (2 x 30.97 g/mol) + (8 x 16.00 g/mol)

= 120.24 g/mol + 61.94 g/mol + 128.00 g/mol

= 310.18 g/mol.

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A compound turns completely into a liquid this observation best describes the physical appearance of a compound when it reaches the end of its melting point range. Here option B is the correct answer.

When a solid compound is heated, it undergoes a process called melting in which it transforms into a liquid state. The melting point of a compound is the temperature at which it changes from a solid to a liquid state. The melting process is characterized by a range of temperatures over which the compound is observed to be partially or fully melted.

The observation that best describes the physical appearance of a compound when the end of its melting point range is reached is B - the compound completely converts to a liquid. At the end of the melting point range, the compound has absorbed enough heat energy to fully overcome the intermolecular forces that hold its constituent particles together in a solid state, resulting in the complete transformation of the compound into a liquid.

This state is characterized by the loss of a crystalline structure, where the particles are free to move about and slide past each other, leading to an increased fluidity and mobility of the compound. At this stage, the compound is fully melted and can be poured or transferred into a new container in its liquid form.

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Complete question:

Which observation best describes the physical appearance of a compound when the end of its melting point range is reached?

A - the compound begins to convert to a liquid.

B - the compound completely converts to a liquid.

C - the compound begins to evaporate.

We can create a buffer solution with a pH of 3.7 by using formic acid as the buffer system's acid component.

To keep fundamental conditions in place, these buffer solutions are used. A weak base and its salt are combined with a strong acid to create a basic buffer, which has a basic pH. Aqueous solutions of ammonium hydroxide and ammonium chloride at equal concentrations have a pH of 9.25. These solutions have a pH greater than seven.

When little amounts of acid or base are supplied, buffers can resist pH changes, because they have an acidic component (HA) to neutralise OH- ions and a basic component (A-) to neutralise H+ ions, they are able to accomplish this.

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The answer is (C) HS.

Each of the other options can donate a proton (act as a Brönsted acid) in certain conditions and accept a proton (act as a Brönsted base) in other conditions. However, HS is only capable of acting as a Brönsted base and accepting a proton, but it cannot donate a proton and act as a Brönsted acid.

Out of the given options, the one that cannot act as both an acid and a base is (C) HS. This is because HS can only act as a brönsted acid by donating a proton to a brönsted base, but it cannot act as a brönsted base by accepting a proton from a brönsted acid. This is because it lacks a lone pair of electrons on the sulfur atom, which is necessary for accepting a proton.

On the other hand, [tex]HCO_{3}[/tex] ,[tex]NH_{4}[/tex]+, and [tex]H_{2}[/tex][tex]O_{4}[/tex]P can all act as both brönsted acids and bases depending on the reaction conditions.

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(B) NH4⁺,  cannot act as both a Brønsted acid and a Brønsted base.

A Brønsted acid is a species that can donate a proton (H⁺), while a Brønsted base is a species that can accept a proton (H⁺).

(A) HCO3⁻ can act as an acid by donating a proton to form CO3²⁻ or as a base by accepting a proton to form [tex]H_{2}CO_{3}[/tex].
(C) HS⁻ can act as an acid by donating a proton to form S²⁻ or as a base by accepting a proton to form [tex]H_{2}S[/tex].
(D) H2PO4⁻ can act as an acid by donating a proton to form HPO4²⁻ or as a base by accepting a proton to form [tex]H_{3}PO_{4}[/tex].

However,
(B) NH4⁺ can only act as a Brønsted acid by donating a proton to form [tex]NH_{3}[/tex] but cannot act as a Brønsted base since it has no lone pair of electrons to accept a proton.

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The volume of the gas when the temperature drops to 270 K and the pressure is 150 N/cm², is 135 cm³

The following data were obtained from the question.

The new volume of the gas can be obtained by using the combined gas equation as illustrated below:

P₁V₁ / T₁ = P₂V₂ / T₂

(100 × 225) / 300  = (150 × V₂) / 270

Cross multiply

300 × 150 × V₂ = 100 × 225 × 270

Divide both side by (300 × 150)

V₂ = (100 × 225 × 270) / (300 × 150)

V₂ = 135 cm³

Thus, the volume of the gas is 135 cm³

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The correct answer is option D. All of the above. It is necessary to slowly add the sulfuric acid to the p-cresol/acetic acid mixture in the test tube to prevent any accidents or injuries.

If sulfuric acid is added too soon, the solution may boil and the acid will spew out of the test tube, perhaps resulting in burns.

Sulfuric acid is also an endothermic reaction, which means it takes energy from its surroundings and has the potential to crystallise or cause the solution to harden.

Last but not least, adding the sulfuric acid gradually enables more precise measurement of the supplied sulfuric acid volume.

It is crucial to gradually add the sulfuric acid to the test tube mixture of p-cresol and acetic acid as a result of all these considerations.

Complete Question:

Why would it be necessary to slowly add the sulfuric acid to the p-cresol/acetic acid mixture in the test tube?

Options:

A.  To ensure accurate measurement of the volume of sulfuric acid added.

B. To prevent the solution from boiling and splattering the acidic solution out of the test tube.

C. To prevent the endothermic reaction from solidifying the solution.

D. All of the above.

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