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3 years ago

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A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 126 g of solutio

n. The reaction caused the temperature of the solution to rise from 21.00 to 24.70 ∘C. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water. Enter your answer in kilojoules per mole of compound to three significant figures.

1 answer:

Karo-lina-s [1.5K]3 years ago

4 0

Answer:

<u>0.976 kJ/mol</u>

Explanation:

A foam coffe cup is considered a perfectly insulated system: heat energy is not exchanged with the surroundings.

Under that assumption, the heat released by the chemical reaction is equal to the heat absorbed by the system.

1. Heat absorbed by the system:

Use the equation Heat = Q = m × C × ΔT, with:

m = 126 g (the amount of solution produced)
C = specific heat of pure water = 4.186 J/gºC
ΔT = increase of temperature = 24.70 ºC - 21.00ºC = 3.70ºC

Q = 126g × 4.186J/gºC × 3.70ºC = 1,951.5J

<em><u></u></em>

<em><u>2. Enthalpy of the reaction</u></em>

The enthalpy must be reported in kJ/mol.

Then, convert juoles to kilojoules, dividing by 1,000; and divide by 2.00 moles, which is the amount of compound that reacted:

ΔHrxn = 1,951.5J × (1kJ / 1,000J) × (1 / 2mol) ≈ 0.9758 kJ/mol

Round to <em>3 significant figures</em>: 0.976 kJ/mol

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Mole fraction of Oxygen=0.381

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The mole fraction may be calculated by means of dividing the variety of moles of 1 element of a solution by the entire quantity of moles of all the additives of a solution. It is cited that the sum of the mole fraction of all of the components inside the solution should be identical to 1.

Mole fraction is a unit of awareness. in the solution, the relative amount of solute and solvents are measured by way of the mole fraction and it's far represented through “X.” The mole fraction is the variety of moles of a selected aspect inside the answer divided by way of the entire range of moles in the given answer.

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The question is incomplete. Please read below to find the missing content.

Assuming that only the listed gases are present, what would the mole fraction of oxygen gas be for each of the following situations? A gas sample of 2.31 atm of oxygen gas and 3.75 atm of hydrogen gas react to form water vapor. Assume the volume of the container and the temperature inside the container does not change.

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2 years ago

Materials expand when heated. Consider a metal rod of length L0 at temperature T0. If the temperature is changed by an amount ΔT

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Answer:

(a) The length at temperature 180°C is 40.070 cm

(b) The length at temperature 90°C is 64.976 inches

(c) L(T, α) = 60·α·T - 9000·α + 60

Explanation:

(a) The given parameters are

The thermal expansion coefficient, α for steel = 1.24 × 10⁻⁵/°C

The initial length of the steel L₀ = 40 cm

The initial temperature, t₀ = 40°C

The length at temperature 180°C = L

Therefore, from the given relation, for change in length, ΔL, we have;

ΔL = α × L₀ × ΔT

The amount the temperature changed ΔT = 180°C - 40°C = 140°C

Therefore, the change in length, ΔL, is found as follows;

ΔL = α × L₀ × ΔT = 1.24 × 10⁻⁵/°C × 40 × 140°C = 0.07 cm

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The amount the temperature changed ΔT = 90°C - 120°C = -30°C

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