chem / gas.mdon commit update practice exams (bf3bb35)
   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 $n={m \over M}$