391.56 Joules
The formula for calculating the amount of heat required is expressed as:
[tex]Q=mc\triangle t[/tex]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
[tex]\begin{gathered} Q=45.3g\times\frac{0.252J}{g^oC}\times34.3^0C \\ Q=391.56Joules \end{gathered}[/tex]Hence the amount of heat required is 391.56 Joules