Discussion Forum

 If the  value of Avogadro number is $6.023\times 10^{23}mol^{-1}$ and the value of Boltzmann constant is $1.380\times 10^{-23}JK^{-1}$, then the number of significant  digits in the calculated value of the universal  gas constant is 

Answer:

Explanation:

Plan. This problem can be solved by using the concept involved in calculation of significant figure.

 Universal gas constant R=kN_A

Where, k= Boltzman constant and N_A = Avogradro number

 $\therefore$    $ R=1.380\times 10^{-23}\times 6.023\times 10^{23}J/K-mol$

    = 8.31174  $\equiv 8.312$

 Since k and N_A both have four significant figures, so the value of R is also rounded off up to 4 significant figures.

  [When  number is rounded off, the   number of significant  figure is reduced, the last digit  is increased by  1 if the following  digits $\geq$ 5 and is left as such it following digits is $\leq$  4]

 Hence, correct integer is (4)