Question

Sodium carbonate (Na2CO3) reacts with acetic acid (CH3COOH) to form sodium acetate (NaCH3COO), carbon dioxide (CO2), and water (H2O). A chemist carries out this reaction in a bomb calorimeter. The reaction causes the temperature of a bomb calorimeter to decrease by 0.985 K. The calorimeter has a mass of 1.500 kg and a specific heat of 2.52 J/g•K. What is the heat of reaction for this system?

Answer 1

Use the formula q=m×Cp×delta T

m=1.500 kg=1,500 g
Co=2.52 J/g·k
delta T=0.985k

q=(1,500g)(2.52 J/g·k)(0.985k)

=3,723.3 J=3.72


I JUST FINISHED THIS QUESTION AND IT SAID THAT THE ANSWER WAS -3.72 kJ SO PUT THAT DOWN AS YOUR ANSWER....I'm not sure why the answer is negative, but this is the most work I can show. If any one knows, why this answer is negative, please advise. Thank you. I hope that this helps :)

Answer 2

Answer:

$\Delta _rH =-3723.3 J$

Explanation:

Hello,

In this case, as you're working in a calorimeter, its associated heat equals the enthalpy of reaction due to the change in the temperature and its mass, in such a way, we compute it as follows:

$\Delta _rH = mCp*\Delta T\\\Delta _rH = 1.500kg * \frac{1000g}{1kg} * 2.52\frac{J}{g*K} * (-0.985K)\\\Delta _rH = - 3723.3 J$

It is negative, since the temperature within the calorimeter is decreased.

Best regards.