Answer:
391.56 Joules
Explanations:
The formula for calculating the amount of heat required is expressed as:

where:
• m is the mass = 45.3g
,
• specific heat of caesium c = 0.252J/gC
,
• change in temperature △t = 120.2 - 85.9 = 34.3 degrees celsius
Substitute the given parameters into the formula

Hence the amount of heat required is 391.56 Joules