Question

Lead melts at 328°c.how much heat is required when 23.0g of solid lead at 297 k condenses to a liquid at 702k?

Answer 1

Answer;

= 1.778 kJ

Explanation;

Considering the following;

Molar mass of lead = 207  

Heat of fusion: 4.77 kJ x mol^-1  

Specific heat: 0.134 J x g^-1xC^-1

Heat required to raise its temp from 297 k to (328+273)k

= 23 × 0.134 × (601-297)

=936 .928 Joules

Heat required to change its state from solid to liquid

= (23/207) moles ×4.77 kJ/mol

= 0.53 kJ or 530 Joules

Heat required to raise the temp from 601 k to 702 k

=23 × 0.134 ×101

= 311.282 Joules

Therefore; 311.282 + 530 + 936.928 = 1778.21 Joules

Thus; = 1.778 kJ