The entropy change accompanying the heating of one mole of helium gas, assuming ideal behaviour, from a temperature of 250 K to a temperature of 1000 K at constant pressure, in `cal K^(-1) "mole"^(-1)` , is
`(ln10 = 2.3, log2 = 0.3)`
`(R = 2 Cal mol^(-1) K^(-1))`

Answer

`6.90`

Explanation

The expression for change in entropy `Delta S` with change in termperature is given by the expression at constant pressure as under:
`DeltaS = C_(p)ln (T_2)/(T_1)` for one mole = `2.303 C_(P) log(T_2)/(T_1)`
`= 2.3xx5/2xxRxxlog (T_2)/(T_1)`
[`C_(P)` for monoatomic gas = `5/2 R`]
`=2.3 xx 5/2 xx 2 xx log (1000)/(250) = 6.9`.