Tear this page out of your laboratory manual and submit it to your TA with your answers. Post-Lab Assessment Questions: Categorize the solids you tested today as pure substance or mixtures. Categorize the pure substances you tested today elements vs compounds and metals vs non-metals. In the lab today you prepared oxygen gas by decomposing hydrogen peroxide. There are many other chemical reactions that generate gases as one of their products. Lets consider the reaction between zinc metal and hydrochloric acid as such an example. a) What are the products of the chemical reaction that occurs when zinc metal is added to an aqueous solution of Hydrochloric acid? b) Write the chemical equation that represents this reaction? c) Write a procedure that explains how you would collect the gas produced from this reaction in the laboratory. Imagine that you are given two metal oxides to study in the lab. You heat each oxide in a small test tube and then insert a glowing splint into each. You observe that the splint in tube 1 immediately ignites and burns with a steady flame before it dies, but the splint in tube 2 does not. a) What happened to the metal oxide in tube 1 when it was heated? b) Do both metal oxides decompose when heated? Provide evidence to support your answer. c) What can you conclude about the stability of the 2 oxides based on these observations?
Describe all of the signs that indicated a chemical reaction occurred.
Describe the temperature change that occurred during this reaction. Is heat required or produced during the reaction?
Describe any other changes that were observed in the steel wool. What reaction might create such a change?
Write a balanced equation for the reaction of the steel wool with oxygen. Be sure to include heat energy in the reaction.
Activity 2: Decomposition Reaction
What gases could be produced from decomposing hydrogen peroxide?
Which gas was produced?
Write a balanced equation for the decomposition of hydrogen peroxide.
Activity 3: Single-Replacement Reaction
What gases could be produced from hydrochloric acid (HCl)?
Which gas was produced?
Write a balanced equation for the reaction of magnesium with hydrochloric acid.
Why did you need to tilt the splint at a 45-degree angle?
a. Write a balanced equation for the reaction initiated by the burning splint.
b. Classify the reaction initiated by the burning splint.
Activity 4: Double-Replacement Reaction
Describe the reaction of sodium bicarbonate and vinegar.
Refer to the section in the Background titled, âStandard Tests Gaseous Products.â Use a flaming splint and a glowing splint to identify the gas above the liquid in the cup. Write the name and formula of the gas in the space provided.
Write a balanced chemical equation for this double-replacement reaction.
One of the two products of this reaction is carbonic acid (H2CO3), which immediately forms water and the gas you identified after exposure to the flaming and glowing splints. Write a balanced equation showing the decomposition of carbonic acid.
Activity 5: Combustion Reaction
Explain why water appears on the inside of the glass test tube.
Write a balanced equation for the combustion reaction.
Activity 6: Precipitation Reaction
Write a balanced equation for the precipitation reaction.
Which product in the above reaction is the precipitate?
Discussion Questions
Predict the product(s) of the following equations. Balance the equations, and classify each of the reactions by type.