Which of the following is a universal constant?

Select the incorrect relation. (Where symbols have their usual meanings)

The specific heat of argon at constant pressure and constant volume are $C_p$ and $C_v$ respectively. Its density $\rho$ at $N.T.P.$ will be: [Where $P$ and $T$ are pressure and temperature respectively at $N.T.P.$]

In the case of a diatomic gas,the fraction of heat supplied at constant pressure that is used for the expansion of the gas is:

The amount of heat needed to raise the temperature of $4 \, \text{moles}$ of a rigid diatomic gas from $0^{\circ} \text{C}$ to $50^{\circ} \text{C}$ when no work is done is ......$R$ ($R$ is the universal gas constant).

What is the molar heat capacity of water? ($R$ is the universal gas constant.)