Relating the Moles & Volume of a Gas

• Hand in labs and pick up your worksheets

Avogadro’s Hypothesis

• Equal volumes of different gases at the same temperature and pressure contain the same number of particles

Standard Temperature and Pressure (STP)• Pressure = 101.3 kPa = 1 atm (pressure at sea level)• Temperature = 25°C • At STP: 1 mol of any gas has a volume of 22.4 L• Conversion factor: 22.4 L/mol• Only for gases and only at STP!• So this is not the same volume as the one in density

unless you are told that it’s a gas and that it is at STP

Practice

• Hebden p.83 #11 a, b and #12 a, b

Think, Pair, Share

• Try the following problems on your own first

• If you have trouble then talk to your partner

• If both of you still do not feel confident, form a group of 4 with another pair

Think, Pair, Share

1) How many chloride ions are in 8.3 g of copper(II) chloride?2) Calculate the number of hydrogen atoms in 4.5 mol of glycerol, C3H5(OH)3.3) How many molecules are in 14.56 g of sodium hydrogen sulfate?

4) Natural gas consists primarily of methane, CH4. What is the mass of 8.0 L of CH4 at STP?

5) What volume of CO2 at STP contains 0.20 g of carbon?

Think, Pair, Share

1) How many chloride ions are in 8.3 g of copper(II) chloride?

CuCl2 molar mass: 63.546+2x35.453 = 134.449 g/mol

8.3g x 1mol/134.449g x 6.022x1023 molec/1mol = 3.717588 x 1022 molec CuCl2

There are 2 Cl atoms for in every 1 molecule of CuCl2

3.717588 x 1022 molec CuCl2 x (2 atom Cl)/(1 molec CuCl2) = 7.4 x 1022 atoms

Think, Pair, Share

2) Calculate the number of hydrogen atoms in 4.5 mol of glycerol, C3H5(OH)3.

C3H8O4.5 mol x 6.022x1023 molecules/mol = 2.7099 x 1024

There are 8 atoms of H for every 1 molecule of C3H8O2.7099 x 1024 x 8 = 2.2 x 1025 atoms

Think, Pair, Share

3) How many atoms are in 14.56 g of sodium hydrogen sulfate?

NaHSO4 14.56g x 1mol/120.0589g x 6.022x1023 = 7.303x1022

atoms

Think, Pair, Share

4) Natural gas consists primarily of methane, CH4. What is the mass of 8.0 L of CH4 at STP?

8.0 L x 1mol/22.4L x 16.0426g/mol = 5.7 g

Think, Pair, Share

5) What volume of CO2 at STP contains 0.20 g of carbon?

0.20g x 1mol/12.011g x 22.4L/mol = 0.37 L