1# Gases 2 3## Comibned gas equation 4 5$${P_1 V_1 \over T_1} = {P_2 V_2 \over T_2}$$ 6 7## Perfect gas equation 8 9$$PV=nRT$$ 10 11where 12$R =$ universal gas constant $= 8.31\text{ J K}^{-1} \text{mol}^{-1}$ 13$P$ is measured in kPa 14$V$ is measured in L 15$T$ is measured in K 16$n$ is no of mol of gas 17 18 19- **Standard temperature and pressure (STP)** - standard temperature is 0 $^\circ$ C or 273 K. Standar dpressure is 100.0 kPa 20- **Standard laboratory conditions (SLC)** - temperature 25 $^\circ$ C (298K), pressure 100.0 kPa 21 22## Molar gas volume 23 24> Equal volumes of all gases measured at the same temperature and pressure contain the same number of gas particles 25 26$\therefore$ 1 mole of any gas at SLC occupies 24.8L - **molar gas volume** 27 28$$n={V \over V_M}$$ 29 30where $n$ = number of mol 31$V$ = actual volume (in litres) 32$V_m$ = molar volume of gas 33 34$$\therefore n_{SLC} = {V \over 24.8}$$ 35 36## Molar volume 37 38Volume of a mole of a gas - depends on pressure & temperature 39Molar gas volume = $V_M = 24.8\text{ L mol}^{-1}$ at SLC 40Use $n = {V \over V_m}$ like $n={m \over M}$