Gen Chem Question

Question

A 1.800 g sample of solid phenol (C6H5OH) was burned in a bomb calorimeter whose total heat capacity is 7.854 kJ/°C. The temperature of the calorimeter plus contents increases from 21.36 °C to 26.37 °C.

(a) Write the balanced chemical equation for the bomb calorimeter reaction (assume all gases).

(b) What is ∆𝐸𝑟𝑥𝑛 per mol of phenol?

Answer 1

The heat of the reaction (delta E) is the delta T multiplied by the heat capacity of the calorimeter. So it is (5.01 degrees C)(7.854 kJ/degree C)=39.349 kJ. We then divide this value by the moles of phenol (1.8 gms/94 grams/mole) and find 0.0191 moles. So 39.349 kJ/0.0191 moles=2060 kJ/mole. The equation is 2C₆H₅OH + 14 O₂--->12 CO₂ + 6H₂O.

Answer 2

So when you are burning phenol, it is a carbon compound that you are burning in oxygen, so that basically means it's a combustion reaction. The basic products of a simple combustion like this (simple carbon compound) would be just some amounts of CO2 and some amounts of H2O.

At this point you almost have the full equation which would be

_C6H5OH(s) + _O2 ----> _CO2(g) + _H2O(g)

Those underscores in front are for you to try to figure out how to balance that equation. You want to keep the amounts of each elements on both sides the same. For example, if I have 6 carbons on the left side of the arrow, I need 6 carbons in total on the right side, too. feel free to ask a follow up if you need more help with this!

part b)

Finding change in energy is simply a matter of plugging into the formula of E= mc(dT) and you already have all three of these values from the question!

m is the mass in grams of the substance, c is the heat capacity and change in T is simply the difference in the temperature. be sure that you also answer in per moles of phenol, which is asking that you find the moles of phenol used here from moles = mass/molarmass equation and divide the energy you just found by that