A sample of K(s) of mass 2.720 g undergoes combustion in a constant volume calorimeter at 298.15 K. The calorimeter constant is 1849 J K−1, and the measured temperature rise in the inner water bath containing 1439 g of water is 1.60 K.

Part A

Calculate ΔU∘f for K2O.

Express your answer to three significant figures and include the appropriate units.

Part B

Calculate ΔH∘f for K2O.

Express your answer to three significant figures and include the appropriate units.

A) The ΔU° of is -361 kJ/mol.

B) The ΔH° of is -362 kJ/mol.

Explanation:

Heat released by the reaction = Heat absorbed by the calorimeter + Heat absorbed by the water

where,

q = heat released by the reaction

= heat absorbed by the calorimeter

= heat absorbed by the water

= specific heat of calorimeter =

= specific heat of water =

= mass of water = 1439 g

= change in temperature =

Now put all the given values in the above formula, we get:

m = mass of substance= 2.50 g

n = moles of substance

According to reaction , 2 moles of K gives 1 mole of

Then 0.06974 moles of K will give:

of

12,591.64 Joules of energy was released when 0.03487 mol of are formed.

So, the enthaply of formation of : ΔU°

The ΔU° of is -361 kJ/mol.

= moles of gases on RHS - moles of gasses on LHS

The ΔH° of is -362 kJ/mol.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.