Exercise 1: Gas and Flame Tests Data Table 1. Gas Observations
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Exercise 1: Gas and Flame Tests
Data Table 1. Gas Observations.
| Step/Reaction | Observations |
| Reaction between zinc and hydrochloric acid | ? |
| Hydrogen Gas + Flame | ? |
| Reaction that occurs when magnesium is in contact with hydrogen peroxide | ? |
| Oxygen Gas + Smoldering toothpick | ? |
| Gas Mixture + Flame | ? |
Questions
A) Write a balanced chemical equation describing the reaction of zinc and hydrochloric acid?
B) What gas was produced by the reaction of zinc and hydrochloric acid? How did this gas behave in the presence of fire?
C) What gas was produced by the decomposition of hydrogen peroxide? What happened when the smoldering toothpick came in contact with the gas?
D) Compare the behavior of the mixture of gases with each solitary gas in the presence of flame?
E) Outline the procedures you would use to determine whether a gas sample was composed of hydrogen or oxygen?
Exercise 2: Gas and Reactions
Data Table 2. Carbon Dioxide Reaction Observations.
| Step/Reaction | Observations |
| Reaction between Ca(OH)2 and CO2 | ? |
| Reaction between CO2 and BTB | ? |
| Carbon Dioxide Gas + Flame | ? |
| Reaction between Ca(OH)2 and Alka-Seltzer® + water gas | ? |
| Alka-Seltzer®/ Water Gas + Smoldering toothpick | ? |
| Reaction between Ca(OH)2 and Breath | ? |
Questions
F) The chemical equation for the reaction of baking soda (sodium bicarbonate, NaHCO3) and vinegar (acetic acid, CH3COOH) may be written as two steps. Fill in the missing information for the chemical equation.
Step 1: ___________ + ___________ ® CH3COONa(aq) + H2CO3(l)
Step 2: H2CO3(l) ® H2O(l) + ___________
G) Write a chemical equation for the reaction of CO2 and limewater (Ca(OH)2). Write a physical description of the products formed.
H) When the bromothymol blue (BTB) was exposed to the CO2 gas, what color was the solution? Did the BTB indicate presence of an acid or base? Explain your answer.
I) Did the reaction between the Alka-Seltzer® and the tap water produce hydrogen, oxygen, or carbon dioxide gas? Support your answer with results from your work in both Exercise 1 and Exercise 2.
J) 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.
K) In 1766, Henry Cavendish became the first scientist to isolate hydrogen. To do so, Cavendish placed a variety of metals in acid. Which of the reactions in this experiment (Exercises 1 and/or 2) most closely mimics Cavendish’s methods?
Expert Answer
Data Table 1. Gas Observations
| step/reaction | obervation |
| Zn+HCl | gas is evolved, Zn dissolves |
| H2(g) + flame | burns visorously |
| O2(g) + smoldering toothpick | vigorous burning |
| Gas mixture + Flame | Burns instantly with heat evolved |
| Mg + H2O2 | Mg dissolves forms a white ppt |
A) balanced chemical equation describing the reaction of zinc and hydrochloric acid
Zn(s) + 2HCl(aq) —> ZnCl2(aq) + H2(g)
B) gas produced by the reaction of zinc and hydrochloric acid and the gas behavior in the presence of fire,
H2(g) produces which burns vigorously in flame
C) gas was produced by the decomposition of hydrogen peroxide and effect of smoldering toothpick came in contact with the gas
O2 gas produced, which burns the toothpick even faster
D) Comparing the behavior of the mixture of gases with each solitary gas in the presence of flame,
Both H2 and O2 are combustible gases or flammable in air in pressence of flame.
E) Outline of the procedures we would use to determine whether a gas sample was composed of hydrogen or oxygen,
H2 burns in air without flame, O2 is stable without flame.
Data Table 2. Carbon Dioxide Reaction Observations
| step/reaction | observation |
| Ca(OH)2 + CO2 | ppt is formed |
| CO2 + BTB | yellow color to solution |
| CO2 + Flame | extinuishes the flame |
| Ca(OH)2 + Alka-Seltzer + water gas | ppt |
| Alka-seltzer/water gas + smoldering toothpick | flame extinguishes |
| Ca(OH)2 + Breath | ppt fo |
F) The chemical equation for the reaction of baking soda (sodium bicarbonate, NaHCO3) and vinegar (acetic acid, CH3COOH) may be written as two steps. Filled the missing information for the chemical equation.
Step 1: CH3COOH(aq) + NaHCO3(s) —-> CH3COONa(aq) + H2CO3(l)
Step 2: H2CO3(l) + H2O(l) + CO2(g)
G) chemical equation for the reaction of CO2 and limewater (Ca(OH)2) and physical description of the products formed.
Ca(OH)2(aq) + CO2(g) —> CaCO3(ppt) + H2CO3(aq)
H) When the bromothymol blue (BTB) was exposed to the CO2 gas, the color becomes yellow of the solution. The BTB indicates presence of an acid which is H2CO3.
I) The reaction between the Alka-Seltzer® and the tap water produce carbon dioxide gas.
citric acid + NaHCO3 —> NaCitrate + CO2 + H2O
J) Based on our observation of the reaction that occurred when limewater was exposed to your breath, CO2 gas was exhaled.
It turns lime water to ppt of CaCO3.
K) In 1766, Henry Cavendish became the first scientist to isolate hydrogen. To do so, Cavendish placed a variety of metals in acid. Which of the reactions in this experiment (Exercises 1 and/or 2) most closely mimics Cavendish’s methods?
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