Dear student ,
It is very important to remember the values of R with their units.
eg. if in the questions from the Gaseous State ; Pressure is given in atm , volume in L , temperature in Kelvin the use:
R= 0.0821 atm L mol-1 K-1.
If you have to find energy (in Joules ) like you are talking about equillibrium questions then use R= 8.314 J mol-1 K-1
If you have to answer in calories then use R= 2 cal mol-1 K-1
Chemistry Consultant
Askiitains