The total energy of one mole of an ideal monoatomic gas at 27C is
 

Dear student , 

                      For these kind of questions , you must know the formula to calculate the energy of ideal monoatomic gas. 

                          Energy is given by $E = \frac{3}{2}\times R\times T$

                   If you want to calculate energy in calories , put R = 2 Cal/K 
                     
                                     This gives total energy $E=\frac{3}{2}\times 2\times 300 = 900 Calories$

Hence total energy of one mole of ideal monoatomic gas is 900 Calories. 


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