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How many calories are required to heat 4...

How many calories are required to heat `40 g` of argon from `40^(@)C` to `100^(@)C` at constant volume? `(R = 2 cal mol^(-1) K^(-1))`

A

1200

B

120

C

180

D

2400

Text Solution

Verified by Experts

The correct Answer is:
C
Heat required to raise the temperature from `40^(@)C` to `100^(@)C` at constant volume is given is
`q = nC_(V) Delta T`
where `n` is the number of moles, `C_(V)` is molar heat capacity and `Delta T` is the temperature change.
`n_(Ar) = ("Mass"_(Ar))/("Molar mass"_(Ar)) = (40 g)/(40 g mol^(-1)) = 1 mol`
For monoatomic gases like argon, `C_(V) = 3 mol^(-1)`. Thus,
`q = (1) (3) (100 - 40)`
`180 cal`
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