I need help with my homework An unknown substance contains 43.20% oxygen, 8.200% hydrogen and 48.60% carbon. Determine the empirical formula.

dH = +90kJ

Given the following chemical reactions with their individual enthalpy change expressed as:

We need the enthalpy change value for the reaction shown:

To get the equivalent reaction from the 2chemical reactions above, we will interchange the product and reactant of the formation of water to have:

Hence the dH value for the following chemical reaction C + 2H2O -> CO2 + 2H2 is +90kJ

What is the wavelength of 101-WCHEM its broadcasting frequency is 101.9 megahertz?

The relationship between the frequency of an electromagnetic wave and its wavelength is given by this formula:

c = λ * f

where, c stands for the speed of light, λ is the wavelength and f is the frequency.

According to our problem:

f = 101.9 megahertz

λ = ??

And we can search for the value of the speed of light:

c = 2.99 * 10⁸ m/s

To solve the problem we have to convert MHz into cycles/sec

1 MHz = 1 000 000 Hz = 1 * 10⁶ Hz

1 Hz = 1 cycle/sec

f = 101.9 MHz * (1 * 10⁶ Hz) / (1 MHz) = 1.019 * 10⁸ Hz = 1.019 * 10⁸ cycles/sec

Our unknown is the wavelength. Let's solve our formula for λ:

λ = c / f

Replacing:

λ = (2.99 * 10⁸ m/s) / ( 1.019 * 10⁸ cycles/s)

λ = 2.93 m

The wavelength of 101-WCHEM is 2.93 m.

If we want to convert it to cm:

100 cm = 1 m

λ = 2.93 m * 100 cm/(1 m) = 293 cm

The wavelength of 101-WCHEM is 293 cm.

H₂O and CO₂ are the substances needed to carry out photosynthesis. Chlorophyll molecules absorb sunlight and break down molecules of H₂O, releasing O₂ and hydrogen. Then, hydrogen binds to CO₂ and forms glucose (C₆H₁₂O₆).

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

So this chemical reaction equation represents Photosynthesis.

Answer:

Explanations:

Given the unbalanced chemical reaction expressed as:

The balanced chemical reaction will be expressed as:

Given the following

Mass of Na = 2.35g

Mass of H2O = 7.25g

Determine the moles of the elements

Moles of Na = Mass/Molar mass

Moles of Na = 2.35/.35

1) First, let's find out how many moles of O are in 1 mol of Ca(NO₃)₂

It has:

1 mol of Ca

If the compound is enclosed in parentheses, you must multiply the value outside the parentheses by each atom of each element that is within the parentheses. In this case the value is 2, so it is necessary to multiply 2x1 (because inside the parentheses there is an atom of N) and multiply 2x3 to find the amount of oxygen (because inside the parentheses there are 3 atoms of O)

2 mol of N

6 mol of O

2) Now let's use the rule of 3 to find out how many moles of O are in 1.9 mol of Ca(NO₃)₂

1.9 mol of Ca(NO₃)₂ ------ x mol of O

1 mol of Ca(NO₃)₂ -------- 6 mol of O

x = 1.9 × 6

x = 11.4 moles of O

Answer: 11.4 mol O

Answer

B. 6.02 x 10²³ molecules CH₄

Explanation

Avogardro's constant says 1 mole of a substance has 6.02 x 10²³ molecules.

⇒ 1 mole = 6.02 x 10²³ molecules/atoms

Therefore, the mole of methane in the given molecules can be calculatedas follows

Hence, what belongs to the green box is 6.02 x 10²³ molecules CH₄

answer and explanation

3.0 grams is converted to gas.

we first find the number of mols

n = m/M

n - mols

m - mass

M - molar mass

n = 3.0/ 28.01

= 0.12 mols

we know that at STP every gas has a volume of 22.4 L

therefor 0.12 mols will have a volume of:

0.12 x 22.4 = 2.69 L

Answer:

Explanation:

Here, we want to balance the given redox reaction in a basic medium

We start by breaking the reaction into half-reactions:

The next step here is to balance the other elements aside from oxygen and hydrogen. We can see, however, that the other elements are balanced. Then we proceed to the next step

We balance the oxygen atoms by adding water molecules:

Now, the next step is to balance the hydrogen by adding hydrogen ions

We have that as:

Now, we balance the charges by adding electrons:

Now, we seek to strike out the electrons. We multiply equations 1 by 3 and 2 by 2:

Balancing this, we have:

1) Write the chemical equation.

2) Convert the mass of Na2SO4 to moles of Na2SO4.

The molar mass of Na2SO4 is 142.0421 g/mol.

3) Moles of NaOH needed

The molar ratio between NaOH and Na2SO4 is 2 mol NaOH: 1 mol Na2SO4.

0.8871 mol NaOH is required to form 63 g Na2SO4.

Given that :

• Mass of C6H12O6 = 9.74g

• Molecular mass C6H12O6 =180.156g/mol

• Moles of C6H12O6 = mass/M.Mass

=9.74g/180.156g/mol

=0.054moles.

(2.1) Carbon → 1 mole C6H12O6 : 6mol C

so, 0.054moles : x mol C

Therefore x mol C = 0.054 * 6 = 0.324moles of Carbon

• Number of atoms for C

No of C atoms = mole* Avogadro number

=0.324 * 6.022*10^23

=1.95x10^23 atoms

(2.2) Hydrogen → 1 mole of C6H12O6 : 12 mol of H

So; 0.054moles : x mol H

Therefore xmol H = 0.054*12 = 0.648 moles of Hydrogen

• Number of atoms for H

No of H atoms = 0.648 * 6.022*10^23

=3.90x10^23 atoms .

(2.3) Oxygen → 1 mole of C6H12O6 : 6 mol of O

So, 0.054 moles : xmol O

Therefore x mol O = 0.054 * 6 =0.324 moles

• Number of atoms for Oxygen =0.324 * 6.022*10^23

=1.95x10^23 atoms

Let's start by stating the important given data:

time ln[A]

0

20

To answer this question, we have to use the following formula corresponding to the first-order reaction rate constant:

Using

Answer

[H₃O⁺] = 1.0 x 10⁻¹² M

Explanation

Given that:

[OH⁻] = 1.0 x 10⁻² M

What to find:

To calculate the [H₃O⁺] of the NaOH solution.

Step-by-step solution:

The [H₃O⁺] of the NaOH solution can be calculated using the relation given below:

[H₃O⁺] x [OH⁻] = 1.0 x 10⁻¹⁴

Therefore, the [H₃O⁺] will be:

Hence, the [H₃O⁺] value of the NaOH aqueous solution is 1.0 x 10⁻¹² M

First, remember that:

1 mol of any compound is the same thing as the molecular mass of the compound.

So, we could say that 1 mol of H2O is equal to the molecular mass of H2O, which is 18.001g/mole.

Given that we have 180g of water, we could write:

Therefore, there are 10 moles of water in 180g of water.

To convert grams to moles, we just divide the amount in grams we have by the molecular mass.

An organic compound with a carboxyl functional group is known as a carboxylic acid. They can be found in abundance in nature and are also synthesized by humans. Carboxylic acids deprotonate to produce a carboxylate anion with the general formula R-COO-, which can be used to make several useful salts including soap.

preparation ---

using Alcohol -(see image)

With the addition of oxidizing agents, primary alcohol is oxidized to produce carboxylic acid. As a result, the oxidation of primary alcohols yields aldehydes, which are then oxidized again to yield carboxylic acids.

using Grignard reagents-(see image)

The Grignard reagents reaction allows for the formation of carboxylic acid. Grignard reagents form carboxylic acid salts when they react with crushed dry ice or solid carbon dioxide.

properties ---

1)Carboxylic acid molecules are polar due to the presence of two electronegative oxygen atoms

2)They also participate in hydrogen bonding due to the interaction of the carbonyl group (C=O) and the hydroxyl group.

To know more about organic chemistry click below

https://brainly.com/question/26088065

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Steel wool and Oxygen (Fire)

Steel wool is mostly iron (Fe) and oxygen cannot be seen but it is used during heating or burning of substances. When iron is burned, it reacts with oxygen in the air to form iron oxide (FeO2). This reaction releases heat. When the steel wool is heated, a new substance is created. The mass of steel wool (product) is increased. This is a chemical change/reaction because the steel wool changes to iron oxide, and mass is not conserved.

Egg and heat

An egg is a liquid substance which consists of colorless substance and yellow yolk. Heat is not seen but produced by the heat source. When the egg is heated, it becomes a solid. The mass of the egg is not changed, it remains the same, the only difference is that it changes from being a liquid to solid. Only a physical change occurred.

Water and heat

Water (I will assume it is in its liquid state) is liquid and heat is the source of energy, it cannot be seen but is implied by the heat source which can be a stove in this case. When liquid water is heated, its state is changed to vapor or gas. The mass of the water remains the same, thus mass is conserved because this is a physical reaction or change.

Zinc and hydrogen Chloride

Zinc is a brittle metal at room temperature and has a silver-greyish appearance. Hydrogen Chloride is a colourless gas at room temperature. When zinc reacts with hydrochloric acid (hydrogen chloride), the metal displaces the hydrogen to form zinc chloride. This is a chemical reaction since zinc increases in mass, thus mass is not conserved.

Sodium hydroxide and Copper sulfate

Sodium hydroxide is a white solid and copper sulfate is a blue solid. When sodium hydroxide reacts with copper sulfate a blue precipitate of copper hydroxide is formed. This is a chemical reaction, thus the mass of one of the reactants will be larger in products. However, mass is conserved if all products are observed/calculated.

In the scientific world, we have different names to describe each step of the scientific method, two definitions which are very close to one another are Scientific Law and Scientific Theory.

Usually Scientific laws are described using mathematical equations and formulas to describe what will happen in a given situation, for example the Gravity Law

Scientific theory will describe how a phenomenon happens, and it is usually done through observations and testing, like the Evolution theory

Therefore the best answer will be letter B

A. The heat required to increase the temperature of an object 1°C

The latent heat is the energy absorbed or released by a body when its temperature changes

the energy absorbed or released during a phase change is the freezing enthalpy or vapor enthalpy depending on the phases

The energy involved when bonds are broken or formed is the formation enthalpy

the energy involved in a chemical reaction is the reaction enthalpy.

Chemistry => Chemical Reactions => Combustion Reaction

A combustion reaction like the one mentioned consists of oxidizing a fuel(CnHm) to obtain CO2 and Water.

We must take into account that during the chemical reaction there is breaking or formation of bonds, but the number of atoms is maintained.

The empirical formula is the simplest way to express a compound, it tells us the proportion in which the elements are in the molecule

To find the empirical formula we must find the number of moles of carbon and hydrogen produced, these moles will be equal to the moles in the reactants.

We will find the moles of the products from the reactants CO2 and Water, we must pass the mass they give us to moles. We have to divide the mass given between the molar mass of each compound.

Molar Mass H2O = 18.01g/mol

Molar Mass CO2 = 44.01 g/mol

Moles of H2O, atoms of H

In the H2O molecule, there are two hydrogen atoms, so the hydrogen atoms present in the products and reactants will be 0.15x2=0.30 H atoms

Moles of CO2, atoms of C

In the CO2 molecule, there is 1 carbon atom, so the carbon atoms present in the products and reactants will be 0.10 x 1 = 0.10 C atoms

We already know how many atoms of carbon and hydrogen we have. We have 0.10atoms of carbon and 0.30 atoms of H.

To find the empirical formula we divide the number of atoms between the smallest number of atoms found, that is, between 0.10. We will have:

So, the empirical formula will have 1 atom of carbon and 3 atoms of hydrogen, which means that the empirical formula will be: CH3

Answer: c. CH3

Explanation:

mass ----> moles ---> representative particles:

To go from mass to moles we usually use the molar mass of the substance or compound that we are working with. Molar mass is expressed in g/mol, so we divide by the molar mass.

mass --> moles: g * 1 mol/(number of g) = mol

To go from moles to representative particles we use Avogadro's number. There are 6.02 *10^23 particles in 1 mol of particles.

moles ---> particles: moles * 6.02 * 10^23 particles /(1 mol) = particles

Then to go from particles to moles we do something similar.

particles---->moles: particles * 1 mol/(6.02 * 10^23 particles) = moles

And to go from moles to grams, instead of dividing by the molar mass we multiply by it.

moles --> mass: moles * number of g/(1 mol) = g

Answer:

mass ----> 1 mol/(number of g) ---> moles ---> 6.02 * 10^23 particles /(1 mol) ----->particles

mass <---number of g/(1 mol) <----- moles <----1 mol/(6.02 * 10^23 particles)<----- particles

The Lewis dot structure is the one that allows us to see all the electrons in the different compounds, as its bonds:

a)

b)

c)

d)

According to the explanation given in the previous session, now we have a similar situation, but now we have steam changing to liquid water and a release of heat and not absorption. The formula will be the same:

Q = m * ΔHv

We have:

m = 1200 grams

ΔHv = 2260 J/g, but since we are releasing energy, this value has to be negative, -2260 J/g

Now we add these values into the formula:

Q = 1200 * -2260

Q = - 2712000 Joules or 2712 Kilojoules

Answer

V2 = 10.95 L

Explanation

Given:

mass 1 = 4.20 g

mass 2 = 2.25 g

volume 1 = 20.5 L

Required: volume 2

Solution

Step 1: Find the number of moles of mass 1 and 2.

For mass 1:

n = m/M where n is the moles, m is the mass and M is the molar mass

n = 4.20g/31.998g/mol

n = 0.131 mol

For mass 2:

n = 2.25g/31.998g/mol

n = 0.070 mol

Step 2: For this problem, we will use the ideal gas law equation

PV = nRT

However, P, V and R are constant

Therefore

V2 = (V1n2)/n1

V2 = (20.5L x 0.070 mol)/0.131 mol

V2 = 10.95 L

Answer

Explanation

ASA from the question implies Acetysalicylic Acid (C₈H₇O₂COOH)

Therefore, a balanced neutralization equation for the neutralization of ASA and NaOH is:

In this question, we have to calculate how many moles of air is in a tire with this following setup of data:

35 L

38 atm

240 K

In order to find the number of moles, we will be using the Ideal gas law formula, which is:

PV = nRT

Where:

P = pressure, 38 atm

V = volume, 35 L

n = number of moles

R = gas constant value, 0.082

T = temperature, 240 K

Now we add these values into the formula:

38 * 35 = n * 0.082 * 240

1330 = 19.68n

n = 1330/19.68

n = 67.6 moles of air are in this tire

Answer

Correct

Explanation

From the balanced chemical reaction, 4 moles of Zn reacted with 10 moles of HNO3 to produced 4 moles, 1 mole, and 5 moles of Zn(NO3)2, N2O, and H2O respectively.

Therefore, comparing the mole of Zn to HNO3, then the derived ratio is correct.

In this question, we have to determine which option will fit best the polar covalent bond definition.

Covalent bonds are by definition a type of bonding in which we will have the share of electrons instead of donating, like ionic bonds. Polar covalent bonds still follow this definition but we will have an unequal sharing, one atom will end up pulling more of the electrons towards its own side, because this atom is more electronegative.

Therefore the best answer will be the 1st answer

This is a stoichiometry problem, where we have an initial amount of reactant and we need to find out how much of the product will we end up with, in order to do that we need to:

1. Set up the properly balanced equation, which the question already provided us

4 NH3 + 3 O2 -> 2 N2 + 6 H2O

2. See how many moles of reactant there are in the given amount of grams, we will do that by using its molar mass

NH3 molar mass = 17g/mol, and we have 45 grams of it

17g = 1 mol

45g = x moles

x = 2.65 moles of NH3

3. Check the molar ratio between the two compounds, this we can see from the balanced equation, the molar ratio between NH3 and H2O is 4:6, this means that for every 4 moles of NH3 in the reaction, we will have 6 moles of water as product, but we have 2.65 moles of NH3

4 NH3 = 6 H2O

2.65 NH3 = x H2O

x = 3.97 moles of H2O, or we can go ahead and round up to 4 moles of H2O

4. Calculate how many grams will be equal to the number of moles that we found out, using the molar mass of H2O

H2O molar mass = 18g/mol

18 g = 1 mol

x grams = 4 moles of H2O

x = 72 grams of H2O

The question requires us to provide the definition of "dimensional analysis".

Dimentional analysis, also called unit-factor method, is the study of the relation between physical quantities based on their units. We can use it to find the unit that a constant should be expressed, for example, or to convert one unit to another.

Let's consider the following example of dimensional analysis: we know the units used for pressure (P), volume (V), temperature (T) and number of moles (n) of a system, and want to find out the unit that the constant of gases (R) should be written considering these quantities.

We know the units for the following quantities:

P --> atm

V --> L

T --> K

n --> mol

Considering the equation for ideal gases, we can rearrange it to find the constant of gases (R):

Now, using the known units for pressure, volume, temperature and number of moles, we can find out the unit that should be used for the constant of gases:

Thus, R should be obtained in atm.L/mol.K

In this question, we have a gas going through a change in temperature and the law that shows the relationship between temperature and volume is Charles's gas Law, which can be presented with the following formula:

V1/T1 = V2/T2

We have:

V1 = 40 L

T1 = 300 K

V2 = ?

T2 = 50 K

Now we just need to add these values into the formula:

40/300 = V2/50

0.1333 = V2/50

V2 = 6.7 Liters will be the new volume