question_answer 86)

  A vessel contains 1.6 g of dioxygen at STP (273.15 K. 1 atm pressure). The gas is now transferred to another vessel at constant temperature, where pressure becomes half of the original pressure. Calculate : (a) volume of the new vessel. (b) number of molecules of dioxygen.

Answer:

    (i) Volume of 1.6 g\[{{O}_{2}}\]  at STP \[=\frac{1.6}{32}\times 22.4=1.12L\] \[{{P}_{1}}{{V}_{1}}={{P}_{2}}{{V}_{2}}\] or         \[1\times 1.12=0.5\times {{V}_{2}}\] or           \[{{V}_{2}}=2.24L\] (ii) Number of molecules = \[\frac{Mass}{molar\,mass}\times 6.023\times {{10}^{23}}\] \[=\frac{1.6}{32}\times 6.023\times {{10}^{23}}\] \[\mathbf{=3}\mathbf{.0115\times 1}{{\mathbf{0}}^{\mathbf{22}}}\]