Date: Name: Class: Experiment 2-2 Report Provide a brief report to the company s

Question

Date: Name: Class: Experiment 2-2 Report Provide a brief report to the company summarizing your findings and recom- mendations. Make sure your report refers to your data and answers the following questions: 1. What ratio of magnesium mass to acid (HCI and H2SO,) concentration will maximize the amount of hydrogen gas and minimize waste? 2. Does the identity of the acid matter relative to hydrogen gas yield? Why or why not? 3. Based on both the experiment results and the current price of sulfuric acid and hydrochloric acid, is either acid a reasonable alternative for hydrogen gas production? Search the Web for updated prices of the acids or use this price listing: 2.5 liters of sulfuric acid = $20.00 and 2.5 liters of hydro- chloric acid = $12.00.

Explanation / Answer

If we see this experiment then w find out that this is limiting reactant problem. In which we have to find the limiting reagent. When we do the reaction of magnesium with hydrochloric acid then it would be like this:

Mg + 2HCl --------------> MgCl2 + H2

This reaction is displacement reaction and we can see that one mole of magnesium is producing 1 mole of hydrogen gas.

IN the reaction between magnesium and sulphuric acid the reaction is:

Mg + H2SO4 -----------------------> MgSO4 + H2

In the same manner, we can see that in this reaction insoluble magnesium salt is prepared and hydrogen gas is produced.

We calculate the number of moles in both the cases.

Reaction between magnesium and sulphuric acid

Moles of Mg = Given mass / molar mass = 0.05 / 24 = 0.0021

Moles of H2SO4 = Molarity of H2SO4 X Volume of H2SO4 (in l)= 0.005 X 2 = 0.01

Mass of H2 from Mg = Moles of Mg X 1 mol of H2 / 1 mol of Mg X Molar mass of H2 / 1 mol of H2

Mass of H2 from H2SO4 = Moles of H2SO4 X 1 mol of H2 / 1 mol of H2SO4 X Molar mass of H2 / 1 mol of H2

Molar mass of H2 = 2.015 g

Reaction of Mg with HCl

Mass of H2 from HCl = Moles of HCl X 1 mol of H2 / 2 mol of HCl X Molar mass of H2 / 1 mol of H2

As we can see from the results the HCl is limiting reagent in the second reaction and in the first reaction limiting reagent is magnesium. If we calculate the mass ratio of magnesium to acid

When we are increasing molarity of sulphuric acid then at one point the reaction stop, the amount of hydrogen gas producing further does not react because amount of magnesium becomes limited, as we can observe from the table, the hydrogen gas producing is double the moles of magnesium and hydrogen gas. The ratio of magnesium mass to acid concentration of sulphuric acid maximises the amount of gas produced and minimizes the waste because there will be no further leftover magnesium or sulphuric acid.

In sulphuric acid maximum ratio is 0.156 in which mass of magnesium is 0.055 and mass of suphuric acid is 0.35g.

And in hydrochloric acid, maximum ratio is 0.38 in which magnesium mass is 0.05 and mass of hydrochloric acid is 0.365g.

Yes the identity of acid matter in production of hydrogen. Since, sulphuric acid has higher concentration of hydrogen than HCl, so it will produce almost twice of hydrogen gas than HCl. So sulphuric acid is better reagent for production of hydrogen gas.

As we know, sulphuric acid has more cost but it will be reasonable because it will produce more hydrogen in less amount, so it will cost less in total, it does not cost more than HCl we are using.

Moles of Mg Moles of H2SO4 Mass of H2 from Mg Mass of H2 from H2SO4 0.0021 0.01 0.00423 0.020 0.0020 0.0081 0.00403 0.016 0.0020 0.0064 0.00403 0.013 0.0019 0.0049 0.0038 0.010 0.0018 0.0036 0.0036 0.0073 0.0023 0.01 0.0046 0.020 0.0021 0.0081 0.00423 0.016 0.0022 0.0064 0.0044 0.013 0.0023 0.0049 0.0046 0.010 0.0023 0.0036 0.0046 0.0073

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