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 $R =$ universal gas constant $= 8.31 \text{J} \text{K}^{-1} \text{mol}^{-1}$ 12$P$ is measured in kPa 13$V$ is measured in L 14$T$ is measured in K 15$n$ is no of mol of gas 16 17 18- **Standard temperature and pressure (STP)** - standard temperature is 0 $^\circ$ C or 273 K. Standar dpressure is 100.0 kPa 19- **Standard laboratory conditions (SLC)** - temperature 25 $^\circ$ C (298K), pressure 100.0 kPa 20 21## Molar gas volume 22 23> Equal volumes of all gases measured at the same temperature and pressure contain the same number of gas particles 24 25$\therefore$ 1 mole of any gas at SLC occupies 24.8L - **molar gas voluem** 26 27$$n={V \over V_M}$$ 28 29where $n$ = number of mol 30$V$ = actual volume (in litres) 31$V_m$ = molar volume of gas 32 33$$\therefore n_{SLC} = {V \over 24.8}$$