How to test for hydrogen gas in a chemical reaction

Exercise 1

CHEM 181 DL1 Identificat ion of Gases

Zn + 2HCI--->ZnCI2 + H2 (gas)

The gas produced is hydrogen, it burns with a popping sound. The decomposition of hydrogen peroxide produces oxygen gas.

1. Write a balanced chemical equation describing the reaction of zinc and hydrochloric acid.

The gas that was produced by the reaction of zinc and hydrochloric acid was Hydrogen gas and zinc chloride. In the presence of fire, hydrogen explodes with a popping sound. The popping sound put out the flame.

2. What gas was produced by the reaction of zinc and hydrochloric acid? How did this gas behave in the presence of f ire?

Copyright 2019 - Hands-On Labs | http://holscience.com 2 / 6

Data Table 1: Gas Observations

The decomposition of hydrogen peroxide produced Oxygen. When the smoldering toothpick came into contact with oxygen, it started burning again and slowly went out.

3. What gas was produced by the decomposit ion of hydrogen peroxide? What happened when the smoldering toothpick came into contact with the gas?

Oxygen mixed with hydrogen; when exposed to a flame made a popping sound. A mixture of gases produce less amount of heat and solitary gases produce a high amount of heat.

4. Compare the behavior of the mixture of gases with each solitary gas in the presence of f lame.

Oxygen mixed with hydrogen; when exposed to a flame made a popping sound. A mixture of gases produce less amount of heat and solitary gases produce a high amount of heat.

5. Outline the procedures you would use to determine whether a gas sample was composed of hydrogen or oxygen.

Copyright 2019 - Hands-On Labs | http://holscience.com 3 / 6

Exercise 2

Chemicals Observations

HCl + Zn

Hydrogen Gas + Flame

Mn + H O

Oxygen gas + Smoldering Toothpick

Gas Mixture + Flame

Bubbled quickly and started to rise to the top.Gas is being released in the form of bubbles.

A chemical reaction occurred where the gas was released quickly. With the smoldering toothpick you heard a popping sound. The flame went out.

2 2 Fizzing and bubbling and water is being displaced into hydrogen gas. The precipitate in the test tube turned a brownish color.

Cloud of water vapor and gas. The toothpick glowed and was reignited.

The tooth pick glowed followed by a popping sound and then the flame went out.

Copyright 2019 - Hands-On Labs | http://holscience.com 4 / 6

Step 1: CH3COOH (aq) + NaHCO3 (s)--->CH3COONa (aq) + H2CO3 (l)

Step 2: H2CO3 (aq) --->H2O (l) + CO2 (g)

If you add them both together :

CH3COOH(aq) + Na2CO3(s) —> CH3COONa(aq) + CO2(g) + H2O(l)

1. T he chemical equation for the reaction of baking soda (sodium bicarbonate, NaHCO ) and vinegar (acetic acid, CH COOH) may be written as two steps. Fill in the missing information for the chemical equation.

Step 1: _____ + _____ → CH COONa(aq) + H CO (aq)

Step 2: H CO (aq) → H O(l) + _____.

3 3

3 2 3

2 3 2

Ca(OH)2 (aq) + CO2 (g) --->CaCO3 (s) + H2O (l)

The reaction took place when a fizzing of CO2 gas released. The limewater turned cloudy with a precipitate. The calcium carbonate was produced as a salt which turned the solution into cloudy precipitate, which shows that CaCO3 is not soluble in water.

2. Write a chemical equation for the reaction of CO and limewater (Ca(OH) ). Write a physical description of the products formed.

2 2

Copyright 2019 - Hands-On Labs | http://holscience.com 5 / 6

Data Table 2: Carbon Dioxide Reaction Observations

When the BTB was exposed to the CO2 gas, BTB is blue and becomes yellow. The color change indicates the presence of an acidic substance. The acid is H2CO3 carbonic acid.

CO2 + H2O —-> H2CO3

3. When the bromothymol blue (BT B) was exposed to the CO gas, what color was the solution? Did the BT B indicate presence of an acid or base?

2

The reaction between the antacid tablet and the tap water produces carbon dioxide gas. The flame test in Exercise 1 with hydrogen peroxide produced a popping sound the flame reignited. In the presence of CO2 gas, the flame was put out on the toothpick quickly. In the chemical reaction that occurs between the antacid tablet and water produces carbon dioxide which was shown by the bubbles that put out the flame completely.

4. Did the reaction between the antacid tablet and the tap water produce hydrogen, oxygen, or carbon dioxide gas? Support your answer with results f rom your work in both Exercise 1 and Exercise 2.

When air is exhaled in limewater, it turns slightly cloudy ; which shows carbon dioxide gas; which is what we exhale when we breath out. The precipitate did not dissolve in the solution. CO2 reacted with Ca(OH)2 to produce CaCO3.

5. Based on your observation of the reaction that occurred when limewater was exposed to your breath, what gas did you exhale? Support your answer with your observations in Data Table 2.

Copyright 2019 - Hands-On Labs | http://holscience.com 6 / 6

Reaction Observations

Ca(OH) + CO

CO + BTB

CO + Flame

Ca(OH) + Antacid/water gas

Antacid/water gas + Smoldering toothpick

Ca(OH) + Breath

2 2 Fizzing occurred and the lime water turned cloudy with precipitate.

2 The blue color solution (BTB) change to yellow.

2 CO2 gas put out the flame on the toothpick quickly with a little re lease of smoke.

2 Slight bubbling

Flame on the toothpick went out quickly releasing a little bit of smoke.

2 Lime water turned cloudy with a precipitate.