1. Warmup Mg(s) + 2 HCl(g)  MgCl2 (aq) + H2 (g))
1. Determine the partial pressure of the hydrogen gas, PH2.
2. Determine the volume of the H2 gas at standard temperature and pressure.
3. Determine the mass of the magnesium ribbon; convert this to moles of Mg.
4. From your answers to #2 and #3, determine the volume of a mole of H2 gas.

2. Another way to count particles
Molar Volume
Another way to count particles

3. Avogadro’s Hypothesis
You may recall:
Under similar conditions of pressure and temperature, equal volumes of gases contain equal numbers of particles
Doesn’t matter what gas
That means one mole of any gas will occupy a specific volume regardless of the gas (ideally)

4. Molar volume
Molar STP=22.4 L (22.4 dm3)
1 mol=22.4 STP

5. Ideal Gas Law At STP 1 mol=22.4 dm3 What about
n mol?
So, at STP, n moles=n(22.4 dm3)

6. Ideal Gas Law Based on the Combined Gas Law Ideal Gas Constant, R
P1=101.3 kPa
V1=n(22.4 dm3/mol)
T1=273 K
P2=P
V2=V
T2=T
Ideal Gas
Constant, R

7. R depends on units

8. Ex: How many moles of hydrogen will occupy 0
Ex: How many moles of hydrogen will occupy 0.90 dm3 at a pressure of 105 kPa and a temperature of -73°C?
V=0.90 dm3
P=105 kPa
T=-73°C +273
200K
R=8.31 kPa*dm3
mol*K
n=?

9. Assignment
Unit 9 WS #2