Question

Please answer all questions in both worksheets! Thank you!

1. What is the ideal gas law? Write the equation below and label all the components of the equation. 2. Write the balanced chemical equation for the reaction between Mg and HCI below include phases of each constituent. Mg + HCI 3. If a student used an excess of HCl to dissolve 0.045 grams of pure Mg ribbon, and collected the gas in a test tube over water how much H2 gas could she produce, calculate the answer in moles. 4. What is the vapor pressure of water at 22 °C, this can be found in your textbook or by doing a Google search. If the total pressure inside the test tube is 1 atm, what is the pressure of the hydrogen gas? This is explained on the first page of the lab. 5. If the volume of gas actually collected was 45 ml and the temperature in the room is 22 °C, how many moles of hydrogen gas is present, use the ideal gas law. For pressure use the pressure of hydrogen gas from #4 above. 6. Calculate the percent error if #3 is the accepted value for moles of H2 and #4 is the experimental value.

Answer 1

1) Ideal gas law

Relates the four variables of gas P, pressure , V volume , T temperature and n, number of moles.

PV = n RT

2) Mg (s) + 2HCl(aq) -------------> MgCl2(aq) + H2(g)

3)

Mg (s) + 2HCl(aq) -------------> MgCl2(aq) + H2(g)

0.045g/24g/mol xs 0 0 initial moles

= 0.001875

0 0 0.001875 0.001875

Thus the moles of H2 formed = 0.001875 mol

4) vpor pressure of water at 22C =19.827 mmHg

pressure inside the H2 tube = 1 atm = 1 atm x 760mmHg /1 atm

Thus the partial prssure of H2 = 760-19.827 =740.173 mmHg

5)

Volume of H2= 45mL = 0.045 L

pressure of H2 = 740.173mmHg = 740.17/760 atm

temperature = T = 22C = 22+273 = 295 K

Using the ideal gas equation PV = nRT

n, moles of H2 = PV/RT = [(740.17/760) atmx0.045L] / 0.0821L.atm/mol.K x 295K

=0.001809 mol

6) percent error = [difference in theoretical and experimental values/ theoretical value] x100

= [0.001875-0.001809]x100/0.001875

= 3.49%