Question

11. Amount of heat energy required to raise the
temperature of 2 g of neon gas by 54°F at constant
volume is [R = 2 cal mol-1 K-]
(1) 30 cal
(2) 15 cal
(3) 9 cal
(4) 20 cal​

Answer 1

answer : option (3) 9 cal.

we have to find the amount of heat energy required to raise the temperature of 2g of Neon has by 54°F at constant volume. [R = 2cal/mol/k]

first change the given temperature change into Kelvin.

using concept ,

tempt. change in °F/180 = tempt. change in K/100

⇒54/9 = tempt. change in K/5

⇒tempt. change in Kelvin, ∆T = 30 K

no of moles = 2g/20g/mol = 0.1 mol

molar heat capacity at constant volume of Ne , Cv = 3R/2 [ because Ne is monoatomic]

now amount of energy = nCv ∆T

= 0.1 × 3R/2 × 30

= 0.1 × 3/2 × 2 × 30

= 9 cal

therefore amount of energy at constant volume is 9 cal.