Question

14.00g of Compound X with molecular formula C4H6 are burned in a constant-pressure calorimeter containing 30.00kg of water at 25°C. The temperature of the water is observed to rise by 5.076°C (You may assume all the heat released by the reaction is absorbed by the water, and none by the calorimeter itself.) Calculate the standard heat of formation of Compound X at 25°C.

.

Answer 1

Q = mc∆T

Q = heat energy (Joules, J), m = mass of a substance (g)

c = specific heat (units J/g∙^oC), ∆ is a symbol meaning "the change in"

∆T = change in temperature (^oC Celcius)

We can use the above formula to calculate the amount of heat used to raise the temperature .

Q = ? m = 30.00kg = 30000 gm  c = 4.184 J/g∙^oC ∆T = 5.076°C

Q = 30000 gm x 4.184 J/g∙^oC x 5.076°C

Q = 637139.52 Joules = 637.139 Kilo Joules

Mass of compound = 14.00 gm

Molecular formula =  C4H6

Molar mass of the compound = 54 g/mol

Moles of the compound = 14 g / 54 g/mol = 0.2592 mol

Standard heat of formation of Compound is known as the amount of heat released by one mole of compound. Let us calculate the same.

The standard heat of formation of Compound X = 637.139 Kilo Joule /0.2592 mol = 2457.538 Kilojoules / Mol