Question

when 1.0 mol of NO(g) forms from its elements, 90.29 kJ of heat is absorbed. How much heat is evolved when 5.40 g of NO decomposes to its elements?

Answer 1

Molar mass of NO = At.mass of N + At.mass of O = 14+16=30 g/mol

Given The amount of heat absorbed for the formation of 1 mol=30 g of NO is 90.29 kJ

So the amount of heat absorbed for the formation of 5.40 g of NO is = ( 5.40x90.29) / 30

                                                                                                  = 16.25 kJ

This the the absorbed amount of heat

So for the decomposition of NO the heat is evolved & this is the reverse of the above value

The amount of heat evolved when 5.40 g of NO decomposes to its elements is 16.25 kJ