In order to estimate the population size of the woodlice in her garden, Jessica used the mark-recapture method: she trapped, marked and released 20 woodlice. Three days later, she trapped 15 woodlice and observed that 10 had marks. Use the following formula to estimate the woodlice population size: population size = 1st sample × 2nd sample ÷ 2nd sample that had been marked.



NEED HELP ASAP!!!!!!

Answer: Oxygen (??)

Explanation: Im not sure but smth like H2O (my brain is not braining T-T)

Answer:

Explanation:

dilute solutions of hydrochloric acid (HCl), sulphuric acid (H₂SO₄), and nitric acid (HNO₃) react with active metals to produce a salt and hydrogen gas.

Active metals react strongly and quickly with other elements and compounds due to the electrons in its structure and its ease of sharing the electrons with other elements.

The most active metals are found in Groups 1  and 2 of the Periodic Table (i.e. the left side), and include lithium, potassium, magnesium, and calcium. Metals such as aluminium, lead, and zinc, are less active than magnesium or calcium, but are generally still labelled as 'active'. Metals such as copper, gold, or silver are inactive and will not react.

Therefore, in the provided question, all the metals listed, except for copper, will produce a metal salt + hydrochloric acid. Copper will not react.

In general:

The molecular formula of the compound, given that it contains 51.39% carbon, 8.64% hydrogen, and 39.97% nitrogen is C₆H₁₂N₄

To obtain the molecular formula, we must first determine the empirical formula. Details on how to obtain the empirical formula is given beloww:

Divide by their molar mass

C = 51.39 / 12 = 4.283

H = 8.64 / 1 = 8.64

N = 39.97 / 14 = 2.855

Divide by the smallest

C = 4.283 / 2.855 = 1.5

H = 8.64 / 2.855 = 3

N = 2.855 / 2.855 = 1

Multiply through by 2 to express in whole number

C = 1.5 × 2 = 3

H = 3 × 2 = 6

N = 1 × 2 = 2

Thus, we can conclude that the empirical formula is C₃H₆N₂

Finally, we shall determine the molecular formula. Details below

Molecular formula = empirical × n = mass number

[C₃H₆N₂]n = 140.22

[(12×3) + (1×6) + (14×2)]n = 140.22

70n = 140.22

Divide both sides by 70

n = 140.22 / 70

n = 2

Molecular formula = [C₃H₆N₂]n

Molecular formula = [C₃H₆N₂]₂

Molecular formula = C₆H₁₂N₄

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The ΔG for the reaction at 298 K and the given partial pressures is -55.53 kJ/mol.

What is ΔG ?

The Gibbs free energy change for a reaction under non-standard conditions can be calculated using the following equation:

ΔG = ΔG° + RTln(Q)

where ΔG is the Gibbs free energy change, ΔG° is the standard Gibbs free energy change, R is the gas constant (8.314 J/(mol·K)), T is the temperature in kelvin, and Q is the reaction quotient.

The reaction quotient, Q, can be calculated using the partial pressures of the gases involved in the reaction:

Q = (P(NH3))² / (P(N2) x P(H2)³)

Plugging in the given values, we get:

Q = (0.75 atm)² / (0.35 atm x 0.30 atm³) = 0.2667

Now we can calculate the ΔG for the reaction:

ΔG = ΔG° + RTln(Q)

ΔG = (-32.8 kJ/mol) + (8.314 J/(mol·K) x 298 K x ln(0.2667))

ΔG = -32.8 kJ/mol + (-22.73 kJ/mol)

ΔG = -55.53 kJ/mol

Therefore, the ΔG for the reaction at 298 K and the given partial pressures is -55.53 kJ/mol.

What is reaction quotient?

Reaction quotient, commonly denoted as Q, is a measure of the relative concentrations of reactants and products in a chemical reaction at a particular moment in time. It is calculated by dividing the concentration of the products raised to their stoichiometric coefficients by the concentration of the reactants raised to their stoichiometric coefficients.

The equation for the reaction quotient Q is similar to the equilibrium constant Kc, but with the concentrations of the reactants and products at any time during the reaction, rather than at equilibrium. When the reaction is at equilibrium, the reaction quotient is equal to the equilibrium constant.

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Answer:

Molecules in the skin are moving faster than molecules in the glass.

Explanation:

Put it in your own words.

Answer:

The energy from the ice transferred to the glass.

A compound formed between two or more non-metal elements that share electrons is called a covalent compound or a molecular compound.

In covalent compounds, the atoms share electrons in order to achieve a full outer shell of electrons and become more stable. Covalent compounds typically have low melting and boiling points, are often gases or liquids at room temperature, and are poor conductors of electricity. Examples of covalent compounds include water (H2O), carbon dioxide (CO2), and methane [CH4].

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The mass of calcium in the original urine sample would be 0.0140 g.

First, we need to find the masses of calcium and magnesium oxalates in the original sample. Let x be the mass of calcium oxalate and y be the mass of magnesium oxalate. Then we have:

x + y = mass of the mixed oxalate precipitate

Next, we need to use the information given to find the mass of calcium in the original sample. The mass of calcium oxide formed after ignition is equal to the mass of calcium oxalate in the original sample. We can calculate the mass of calcium oxide using the mass of calcium carbonate formed and the molar mass ratio of calcium carbonate to calcium oxide.

The balanced chemical equations for the reactions are:

CaC2O4 -> CaCO3 + CO2

CaCO3 -> CaO + CO2

The molar mass of CaCO3 is 100.09 g/mol, and the molar mass of CaO is 56.08 g/mol.

From the given information, we have:

0.0433 g = (x + y)(100.09 g/mol + 80.15 g/mol) / (128.10 g/mol + 80.15 g/mol)

0.0285 g = x(56.08 g/mol) + y(40.31 g/mol)

Solving these equations simultaneously, we get:

x = 0.0140 g

y = 0.0053 g

Therefore, the mass of calcium in the original sample (which is equal to the mass of calcium oxide formed after ignition) is:

0.0140 g

So the mass of calcium in the original sample is 0.0140 g.

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The maximum mass of carbon dioxide that could be produced from 6.9 g of octane and 42.2 g of oxygen is 21.3 g, rounded to 2 significant digits.

What is Octane?

Octane is a hydrocarbon with the chemical formula [tex]C_{8} H_{18}[/tex] It is an organic compound belonging to the alkane group, which means it consists of only carbon (C) and hydrogen (H) atoms bonded together by single covalent bonds. Octane is a colorless liquid with a molecular weight of approximately 114 g/mol and is commonly used as a component in gasoline or fuel for internal combustion engines.

From the balanced equation, we know that 1 mole of octane reacts with 12.5 moles of oxygen to produce 8 moles of carbon dioxide. Therefore, 0.0605 mol of octane would require 0.0605 mol x 12.5 = 0.75625 mol of oxygen to fully react.

Since we have only 1.32 mol of oxygen, which is in excess compared to the 0.75625 mol required by octane, oxygen is the excess reactant, and octane is the limiting reactant.

Now, we can use the stoichiometry of octane to carbon dioxide to calculate the maximum mass of carbon dioxide produced:

From the balanced equation, we know that 1 mole of octane produces 8 moles of carbon dioxide.

Molar mass of carbon dioxide (CO2) = 44.01 g/mol

Maximum moles of carbon dioxide produced from octane = 0.0605 mol x 8 = 0.484 mol

Maximum mass of carbon dioxide produced from octane = 0.484 mol x 44.01 g/mol = 21.3 g

Remember to round the final answer to 2 significant digits as requested.

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The molality of the solution is 1.080 mol/kg of a 48 grams of MgCl2 is dissolved in 500g of water, density of water = 1 kg/1L.

Taking the moles of solute and dividing it by the kilograms of solvent yields the molality of a solution.

Molality is calculated as follows: kg of solvent/kg of solute

500 g, or 0.500 kg, is the mass of the solvent.

MgCl2 molecular weight divided by its mass gives the amount of moles.

48 g / 95.2 g m o l 1 equals the quantity of moles of magnesium chloride.

0.504 moles of MgCl2 are present in one mole.

Molality is calculated as 0.504moles per kilogram.

Molality is equal to 1.080 mol k g 1.

As stated in the definition, molality is the "total moles of a solute contained in a kilogram of a solvent." The terms "molality" and "molal concentration" are synonymous. It is a measurement of a solvent.

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A concentrated saltwater solution weighing 29.97 g and fitting into a flask to the mark of 25.0 ml has a density of about 1199.2 g/L.

By dividing the solution's mass by its volume, we may get its density: density = mass/volume

We need to know the density of water at the solution's temperature as well as the capacity of the flask up to the 25.0 ml level in order to calculate the volume of the solution.

Since 1 mL = 0.001 L, volume is equal to 25.0 mL, or 0.0250 L.

Now, we may determine the solution's density as follows:

1199.2 g/L or 29.97 g/0.0250 L is what is referred to as density.

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The amount that would remain, given that 3 half-lives has pass when you started with 20.0 g is 2.50 grams (1st option)

The following data were obtained from the question:

The amount remaining can be obtained as shown below:

N = N₀ / 2ⁿ

N = 20 / 2³

N = 20 / 8

N = 2.50 grams

Thus, we can conclude from the above calculation that the amount that would remain after 3 half-lives to pass is 2.50 grams (1st option)

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Answer:

2.50g

Explanation:

Answer: The units for molarity are moles/liter.

Similarly, the equation to find molarity is moles divided by liters.

Explanation:  

mol / L is a unit of molar concentration. These are the number of moles of dissolved material per liter of solution. 1 mol / L is also called 1M or 1molar. Mol / m3 is also a unit of molar concentration.

Molarity is expressed in units of moles per liter (mol / L). This is a very common unit, so it has its own symbol, which is the uppercase M. A solution with a concentration of 5 mmol / l is called a 5 M solution or has a concentration value of 5 mol.

The molar concentration of the solution is equal to the number of moles of the solute divided by the mass of the solvent (kilogram), and the molar concentration of the solution is equal to the number of moles of the solute divided by the volume of the solution (liter). increase.

463.5 grams of HCl are required to react with 6.35 moles of CaCO₃.

Mass of one mole of substance is referred to as the molar mass. The molar mass of a substance can be calculated by adding up the atomic masses of all the atoms in a molecule.

Balanced chemical equation for the reaction between calcium carbonate (CaCO₃) and hydrochloric acid (HCl) is: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

6.35 mol CaCO₃ * 2 mol HCl / 1 mol CaCO₃ = 12.7 mol HCl

Now, we use the molar mass of HCl (36.46 g/mol) to convert from moles to grams: 12.7 mol HCl * 36.46 g/mol = 463.5 g HCl

Therefore, 463.5 grams of HCl are required to react with 6.35 moles of CaCO₃.

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To convert to Celsius, we subtract 273.15 from the Kelvin temperature, giving us a final answer of 42.1°C.

Temperature is a physical quantity that measures the average kinetic energy of the particles in a system. It is an important parameter for understanding the behavior of matter and the underlying physical processes at work. Temperature is measured in units such as degrees Celsius (°C), Fahrenheit (°F), Kelvin (K), or Rankine (°R). Temperature affects the rate at which chemical reactions occur and the movement of particles in solids, liquids, and gases.

The ideal gas law states that PV = nRT,
where n is the number of moles,
P is the pressure,
V is the volume, R is the ideal gas constant (8.314 J/molK), and
T is the temperature in Kelvin.
Rearranging the equation, we get T = (PV)/(nR).
Plugging in our values, we get T = (89.9 atm * 4191 mL)/(2.6 mol * 8.314 J/molK) = 115.2 K.
To convert to Celsius, we subtract 273.15 from the Kelvin temperature, giving us a final answer of 42.1°C.

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Enantiomers rotate the plane of polarized light in opposite directions, and this property is used to distinguish between them in a process called optical rotation.

Enantiomers are pairs of molecules that are non-superimposable mirror images of each other.

They are isomers, meaning they have the same molecular formula and connectivity but differ in their three-dimensional arrangement of atoms in space.

Enantiomers exhibit identical physical and chemical properties, except for their interaction with plane-polarized light (a type of light that oscillates in a single plane).

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The compound's boiling point is around 73.65 °C.

Unexpected Responses. Favorable reactions are those that cause the system's enthalpy to drop while its entropy rises. The reaction happens naturally when both of these conditions are true. Both endothermic and exothermic reactions, which absorb heat and release it, can occur spontaneously.

We can use the Gibbs-Helmholtz equation to solve for the boiling point:

ΔG = ΔH - TΔS

At boiling point, ΔG = 0, so we can solve for T:

T = ΔH/ΔS

Substituting the given values:

T = (32.77 kJ·mol−1) / (94.72 J·mol−1·K−1)

T = 346.8 K

Converting to Celsius:

Boiling point = 346.8 K - 273.15 = 73.65 °C

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I think it is Ba since the radius increases along the group.but decreases along the period

Answer:

Ba

Explanation:

Ba

At 40°C is the temperature at which saturated solutions of potassium nitrate and sodium nitrate contain the same weight of solute per 100 mL of water contain the same weight of solute per 100 mL of water.

Temperature is a unit of warmth or coldness that can be defined in the context of any number of arbitrary scales. It indicates the direction that heat energy will naturally flow, i.e., through a hotter (body) to a colder (body) body.

Temperature is not the same as the energy in a thermodynamic system; for instance, an iceberg has a significantly larger total heat energy than a match, despite the fact that a match is burning at an extremely high temperature. At 40°C is the temperature at which saturated solutions of potassium nitrate and sodium nitrate contain the same weight of solute per 100 mL of water.

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The sandwich contains approximately 71.25 grams of carbohydrates.

Calories are a unit of measurement used to quantify the amount of energy contained in food and beverages. The number of calories in a particular food is determined by the amounts of carbohydrates, fats, proteins, and other nutrients it contains.

To determine the number of grams of carbohydrates in the sandwich, we need to use the fact that carbohydrates, fats, and proteins have different calorie densities. Specifically, carbohydrates and proteins each contain about 4 calories per gram, while fats contain about 9 calories per gram.

First, let's calculate the total number of calories coming from the fat and protein in the sandwich:

Total calories = calories from carbohydrates + calories from fat + calories from protein

475 Calories = calories from carbohydrates + 10g x 9 Calories/g + 25g x 4 Calories/g

475 Calories = calories from carbohydrates + 90 Calories + 100 Calories

475 Calories - 190 Calories = calories from carbohydrates

285 Calories = calories from carbohydrates

Now that we know the number of calories from carbohydrates, we can use the calorie density of carbohydrates to determine the number of grams of carbohydrates:

285 Calories = carbohydrates in grams x 4 Calories/g

71.25 g = carbohydrates in grams

Therefore, the sandwich contains approximately 71.25 grams of carbohydrates.

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Answer:

strength in ionic compounds.

Explanation:

:)

Lattice energy is an estimate of the bond of strength. It denotes the amount of energy required to break down one mole of a solid ionic compound into its constituent gaseous ions.

The strength of an ionic compound's ionic bonds is measured by lattice energy. It explains several properties of ionic solids, including their volatility, solubility, and hardness. An ionic solid's lattice energy cannot be measured directly.

The higher an ionic compound's lattice energy, the more difficult it is to disassemble the crystal lattice structure and dissolve it in water. As a result, compounds with high lattice energies are less soluble in water than those with low lattice energies.

The value of lattice energy is determined by the charges on the two ions as well as the distance between them. The distance between the ions is directly proportional to their size.

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Complete question:

Lattice energy is an estimated bond of the bond:

A. conductivity

B. group

C. length

D. strength

Choose the correct option.

5,250. The number was rounded up from 5,249 because the last digit, 9, is greater than or equal to 5.

Rounding up is a mathematical operation that involves increasing a number to its nearest whole number. It is commonly used when dealing with money, measurements, or statistics. When rounding up, the number is increased to the next highest whole number. For example, if a number is 6.7, it would be rounded up to 7. Rounding up is often used when dealing with exact measurements or estimates to simplify the calculations. It can also be used to make the results of a calculation easier to understand. In the case of money, rounding up can be used to round a number to the nearest dollar. This prevents dealing with fractional amounts of money. Rounding up can also be utilized in statistical analysis, such as in the calculation of mean or median. This simplifies the data and prevents dealing with fractions or decimals.

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Answer:

The answer is B: 0.0025 M

According to molar concentration and dilution concept, the  [H₃O+] in the final solution is closest to 0.05 M.

Molar 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 molar concentration is moles/liter.

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

In terms of moles, it's formula is given as molar concentration= number of moles /volume of solution in liters.In case of 2 solutions concentrated and diluted it is calculated as, M₁V₁=M₂V₂ substitution gives M₂=0.25×100/500=0.05

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The reaction [tex]2NH_3=N_2H_4+H_2[/tex] has a standard reaction free energy of -62.4 kJ/mol.

Energy is the capacity to carry out tasks or affect change. It comes in a variety of shapes and sizes, including kinetic energy (energy of motion), potential energy (stored energy of position), thermal energy (heat), electrical, chemical, and nuclear energy. Energy is required for the survival and growth of all living things. Additionally, it is necessary for the operation of industries and equipment.

Equation can be used to get a reaction's standard reaction free energy.

ΔG°rxn = ΣΔG°f (products) - ΣΔG°f (reactants).

For the reaction [tex]2NH_3=N_2H_4+H_2[/tex], the ΔG°f values are as follows:

ΔG°f ([tex]2NH_3[/tex]) = -46.2 kJ/mol

ΔG°f ([tex]N_2H_4[/tex]) = -20.8 kJ/mol

ΔG°f ([tex]H_2[/tex]) = 0 kJ/mo

The equation yields the average reaction free energy (ΔG°rxn) of the reaction is:

ΔG°rxn = (2 x -20.8) - (-46.2)

            = -62.4 kJ/mol

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The pH of .3 M NH, where is K = 1.7 x 10^-5 is 11.87 calculated from the equation of dissociation constant.

Kb= [A] /[A + ][X− ]

​1.7×10 −5 = x ^2 /0.3

⇒x= 7.5 ×10 −3

∴[OH − ][H + ]=7.5 ×10 −3

[H + ] =10 ^−14 ⇒pH=11.87

When describing the acidity or basicity of an aqueous solution, chemists use the pH scale, which is also known as acidity and previously stood for "potential of hydrogen". Greater pH values are seen in basic or alkaline solutions than acidic solutions.

Potential hydrogen is the meaning of the acronym pH, which indicates how much hydrogen is present in liquids and how active the hydrogen ion is.

As a first step, we shall ascertain the pKa of the solution before calculating its Ka. When a solution reaches the equivalence point, its pH and pKa are equal. So, by using a titration curve and the Ka = - log pKa equation, we may rapidly ascertain the value of Ka.

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Because it is not very effective at transferring [tex]H^{+}[/tex] ions to water, vinegar is a weak acid. Less than 0.4% of the [tex]CH_{3}CO_{2}H[/tex]molecules in a 1 M solution interact with water to create [tex]H_{3}O^{+}[/tex]and [tex]CH_{3}CO_{2}^{-}[/tex] ions. More than 99.6% of the acetic acid molecules are still whole.

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