Specific heat of `Li(s),Na(s),K(s),Rb(s)` and `Cs(s)` at `398K` are `3.57,1.23,0.756,0.363` and `0.242 J g^(-1)K^(-1)` respectively. Compute the molar heat capacity of these elements and identify any periodic trend. If there is trend, use it to predict the molar heat capacity of `Fr`.

Explanation

Molar heat capacity of `Li(s)`
`=3.57xx6.919=24.8 J mol^(-1) K^(-1)`
Molar heat capacity of `Na(s)`
`=1.23xx22.99=28.3 J mol^(-1) K^(-1)`
Molar heat capacity of `K(s)`
`=0.756xx39.102=29.6 J mol^(-1) K^(-1)`
Molar heat capacity of `Rb(s)`
`=0.363xx85.47=31.0 J mol^(-1) K^(-1)`
Molar heat capacity of `Cs(s)`
`=0.242xx132.90=32.2 J mol^(-1) K^(-1)`
Extraplotting gives
Molar heat capacity of `Fr` will be
`=33.5 J mol^(-1) K^(-1)`