25℃、一定圧力の下、酸素 1.00 mol と窒素 4.00 mol を混合した。両気体は当初隔壁を隔てて別々の部屋に入れられており、隔壁を取り去ったところ圧力は混合前と同じ圧力ｐであった。この混合に伴うエントロピー変化(J/K)を小数点以下1桁まで求めなさい。なお酸素、窒素、混合気体は全て理想気体とし、気体定数RはR = 8.31 J/(K mol)とする。

Oxygen gas (1.00 mol) and Nitrogen  gas (4.00 mol) were mixed under a constant pressure (p) at 25 ℃. Each gas was stored separately. The pressure was kept constant (p) before and after mixing. Answer the entropy change (J/K) of this mixing to the first decimal place. All gases can be treated as an ideal gas and gas constant R is R = 8.31 J/(K mol).