Question

Amount of H2) Displaced for each Trial - Grams of Solute used

Trial	Barometric Pressure	Temperature C	Mass of Chemical	Water Displaced
Trial 1 NaHCO3	1.006973	20.1	1.1 g	.059 L
Trial 2 NaHCO3	1.006973	20	2.0 g	.087 L
Trial 3 Na2CO3	1.006973	22	1.2 g	.044 L
Trial 4 Na2CO3	1.006973	20	1.1 g	.036 L

Use this data to calculate the molar mass:

Trial 1 - Sodium Bicarbonate

Trial 2 - Sodium Bicarbonate

Trial 3 - Sodium Carbonate

Trial 4 - Sodium Carbonate

What is the average experimental volume calculated for sodium carbonate and sodium bicarbonate?

What is the percent error in your calculation?

Answer 1

Calculation of molar mass of NaHCO3

moles of H2 = PV/RT

Trial 1

moles of H2 = 1.006973 x 0.059/0.08205 x (20.1 + 273) = 0.0025 mol

1 mole of NaHCO3 gives 1 mole of H2

molar mass = 1.1/0.0025 = 440 g/mol

Trial 2

moles of H2 = 1.006973 x 0.087/0.08205 x (20 + 273) = 0.0036 mol

1 mole of NaHCO3 gives 1 mole of H2

molar mass = 2/0.0036 = 548.83 g/mol

Trial 3

moles of H2 = 1.006973 x 0.044/0.08205 x (22 + 273) = 0.0018 mol

1 mole of NaHCO3 gives 1 mole of H2

molar mass = 1.2/0.0018 = 666.67 g/mol

Trial 4

moles of H2 = 1.006973 x 0.036/0.08205 x (20 + 273) = 0.0015 mol

1 mole of NaHCO3 gives 1 mole of H2

molar mass = 1.1/0.0015 = 733,33 g/mol