Question

In an experiment, 1.75 g sample of acetic acid, CH3COOH, was burned in oxygen in a calorimeter. The calorimeter contained 925g of water and had a heat capacity of 2.53 kJ/°C. the temperature of the calorimeter and its contents increased from 22.2°C to 26.5°C. use these data to determine the molar heat of combustion of acetic acid? (specific heat capacity of water = 4.18 kJ/Kg·°C) Show ALL Work

Answer 1

To find the molar heat of combustion for acetic acid, calculate the heat absorbed by both the water and calorimeter, then divide the total heat by the moles of acetic acid to get the molar heat of combustion.

Step-by-step explanation:

To determine the molar heat of combustion of acetic acid (CH3COOH), first calculate the total heat absorbed by the calorimeter and water using the formula q = mcΔT for the water and q = CΔT for the calorimeter. Here, m represents the mass of the water, c is the specific heat capacity of water (4.18 kJ/Kg°C), ΔT is the change in temperature, and C is the heat capacity of the calorimeter.

The calculation for water is:

1. qwater = (925 g) x (4.18 kJ/kg°C) x (26.5°C - 22.2°C)

The calculation for the calorimeter is:

1. qcalorimeter = (2.53 kJ/°C) x (26.5°C - 22.2°C)

Next, sum the heat absorbed by both water and the calorimeter to find the total heat released:

qtotal = qwater + qcalorimeter

Then, calculate the molar heat of combustion by dividing the total heat by the amount of acetic acid in moles:

1. ΔHcomb = qtotal / moles of CH3COOH

The number of moles of acetic acid can be found using the molar mass of acetic acid. Finally, remember that the molar heat of combustion should be reported with a negative sign since it is an exothermic process.

Answer 2

First, we determine the amount of energy released by the combustion of the given amount of acetic acid, which can be calculated using:
Energy = mass * specific heat capacity * change in temperature
Q = 925 * 4.18 * (26.5 - 22.2)
Q = 16,626 Joules = 16.6 kJ

Now, the amount of acetic acid available was 1.75 grams. We convert this into moles using:
Moles = mass / molecular mass
Moles = 1.75 / 60
Moles = 0.03 mol

The heat of combustion is:
16.6/0.03
553.3 kJ per mole