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Hydrogen from Zinc and Hydrochloric Acid Experiment

This is the background

Robert Boyle found that, under isothermal conditions (constant temperature), the pressure of a gas is inversely proportional to its volume.

This also means that the product of the pressure and volume is a constant. The equations that describe this relationship are:

P*V= constant

P1V1 = P2V2

Jacques Charles found that the volume of a gas under isobaric conditions (constant pressure) is directly proportional to its temperature. As the temperature increases so does the volume that the gas occupies.

The equations that describe this relationship are:

V/T= constant


V1/T1 = V2/T2

It is possible to combine Boyle's law and Charles' law into a combined gas law:

P1*V1/T1 = P2*V2/T2

The Ideal Gas Law includes the dependence of the volume on the number of gas moles, and an experimentally determined Universal Gas Constant, R.

This law is written as follows:

(P*V) / (n*T) = R (the ideal gas constant)


P*V = n*R*T

The accepted value for R is 8.314472 J/mol*K (Joules per mole per degree Kelvin).

One important result of the Ideal Gas Law is that under constant conditions of pressure and temperature, one mole of any gas will always occupy the same volume. For example, at one atmosphere, the molar volume of an ideal gas would be 22.414 L/mol at 0C and 24.137 L/mol at 21C.

The volume that one mole of an ideal gas occupies when held at a specific temperature and pressure is referred to as a "molar volume". Most gases follow the Ideal Gas Law closely at atmospheric pressure and room temperature.

In this experiment you will determine the molar volume of hydrogen and compare it with the expected ideal gas law value. Hydrogen gas is produced in the reaction:

Zn(s) + 2HCl(aq) -> ZnCl₂(aq) + H₂(g)

It is easy to calculate the number of moles of H₂(g) produced since it is the same as the number of moles of zinc used in the reaction. Knowing the number of moles of H₂(g) produced and measuring the volume that it occupies, one can calculate the molar volume of the gas at room temperature and pressure according to the equation:

Molar volume = measured volume / number of moles (L/mol)

This is the lab procedure

Take an Erlenmeyer flask from the Glassware shelf and place it on the workbench.

2. Add 0.25g of zinc to the Erlenmeyer flask

3. Open the Properties window and click on the Erlenmeyer flask. Click the Open/Close icon in the Properties window to close the flask with an air-tight stopper

4. Take a thermometer and pressure gauge from the Tools shelf and attach them directly to the flask. Record the initial temperature and pressure

5. Add 10 mL of 6M HCl solution to the flask. The HCl is added as if by a syringe piercing the rubber stopper, maintaining the air-tight seal

6. Watch for evidence of the reaction between the zinc and HCl. Record all of the indications that the reaction has occurred

7. The temperature will slowly fall as the flask cools. While you are waiting, take a gas piston from the Glassware shelf and place it on the workbench

8. Once the flask has cooled down to room temperature (21C), disconnect the thermometer and pressure gauge from the flask

9. Drag the flask and drop it onto the gas piston. This connects the two and allows gas to flow from the flask into the gas piston until the pressure equalizes. What pressure is that? If you need to, connect a pressure gauge to the gas piston and measure the pressure inside it

10. Open the Data window, click on the gas piston and record the volume of gas that is contained in the gas piston

11. Repeat the experiment with a new flask and gas piston, using 0.25g of zinc and 20 mL of HCl.
Doc attached. I do not know how to do the calculations.

These are the results of the lab

Add 0.25g Zinc to the Erlenmeyer flask -150mL
Chemicals inside:
1. Zn
2. O2 moles: 0.01243, vol; 149.96mL
3. N2 moles: 0.004972, vol: 149.96mL
Then it is sealed tight with a rubber stopper
Then I take a thermometer and pressure gauge and recorded
Thermometer 21 degrees celsius
Pressure (PSI) 14.697
Then I add 10mL of 6M HCl solution to the flask
And I am spose to record the reaction that takes place
As the temp falls back to 21 degrees Celsius I connect the flask to the gas piston-250mL until the pressure equalizes and what is that pressure.
I then record the volume of gas that is contained in the gas piston and that is
Pressure-gas piston
And the chemicals left inside are
1. O2, moles: 0.000524, vol:102.14mL
2. N2, moles: 0.002096, vol: 102.14mL
3. H2 no data

Then repeat the experiment with a new flask and gas piston using 0.25g of Zinc and 20ml 6M of HCl and after the pressure in the gas piston these are the results
Chemicals left inside of the gas piston
1. O2, moles: 0.001159, Vol; 226.33mL
2. N2, moles: 0.004637 Vol 226.33mL


Solution Summary

A hydrogen from zinc and hydrochloric acid experiment is explained.