Experiment 1: Mass of Zinc: 0.25g 6 M HCl solutions: 10mL Volume of hydrogen gas

Question

Experiment 1:

Mass of Zinc: 0.25g

6 M HCl solutions: 10mL

Volume of hydrogen gas produced is 92.3mL

Temperature: 21.5C

Pressure: 1.00atm

Reaction: Bubbles

Temperature after reaction: 27.4C down to 21.5C

Pressure after reaction: 1.68atm, after 1.66atm

1. How many moles of zinc reacted with the 6M HCl in the first part of the experiment? To find the moles of zinc you need to convert from the grams of zinc to the moles of zinc using the following calculation: moles of Zn = g of zinc * (1 mol Zn/molecular weight of Zn)

2. How many moles of H2 were produced in the first part of the experiment? Notice from the reaction given in the procedures that for every mole of zinc, there is one mole of H2 produced.

3. Based on the ideal gas law, what volume of hydrogen gas do you predict would be evolved given the number of moles of zinc and the temperature and pressure in the room during the first part of the experiment? The formula of the ideal gas law is PV=nRT and you can rearrange the equation in order to solve for the volume as follows V= nRT/P (V is the volume, n is the number of moles, R is the gas constant 0.08206 atm*L/mol*K, and T is the temperature in Kelvin (Kelvin = oC + 273.15).

4. You have recorded the volume of hydrogen gas produced in the reaction and you have calculated the number of moles used in the first part of the experiment. Based on this information, what is the molar volume of hydrogen gas at room temperature? To calculate this, use the formula: Molar volume (L/mol) = (measured volume)/(number of moles). Remember to convert your measured volume from mL into L (1L = 1000mL). Choose the closest answer.

Thank you!

Explanation / Answer

1. How many moles of zinc reacted with the 6M HCl in the first part of the experiment?

0.25g Zn

V = 10 ml

M = 6M

Moles of Zn = mass/MW = 0.25/65.4 = 0.00382 mol of Zn reacted

2. How many moles of H2 were produced in the first part of the experiment? Notice from the reaction given in the procedures that for every mole of zinc, there is one mole of H2 produced.

Reaction

Zn + 2HCl --> ZnCl2 + H2

1 mol of Zn will give 1 mol of H2, therefore, if raito is 1:1; we produced 0.00382 mol of H2

3. Based on the ideal gas law, what volume of hydrogen gas do you predict would be evolved given the number of moles of zinc and the temperature and pressure in the room during the first part of the experiment?

Assume idel gas law

Pv = nRT

V = nRT/P

T = 21.5 + 273 = 294.5

V = (0.00382)(0.082)(294.5)/1 = 0.09225 L or 92.25 ml

4. You have recorded the volume of hydrogen gas produced in the reaction and you have calculated the number of moles used in the first part of the experiment. Based on this information, what is the molar volume of hydrogen gas at room temperature?

Molar volume = Volume per unit mol

V = 92.25 ml or 0.09225 L

mol = 0.00382 mol

V/mol = 0.09225 / 0.00382 = 24.15 L/mol

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