Chapter Six Test: Compounds And Elements
Questions and Answers
- 1.
Answer in complete sentences and explain your reasoning for credit. 10cm3 of hydrochloric acid were poured into eight evaporating dishes. Different amounts of Zinc were added to each dish and left until the reaction stopped. Each solution was then evaporated to dryness, and the mass of the residue (zinc chloride) was determined. Class data were graphed as shown below. If 6.0 g of zinc had been used in the experiment, what would be the mass of zinc chloride formed?
- 2.
Answer in complete sentences and explain your reasoning for credit. Why does this ‘curve’ become horizontal?
- 3.
Answer in complete sentences and explain your reasoning. A student heated 3.0 g of powdered copper in air until the mass was 3.4 g. Why did the copper gain mass when it was heated?
- 4.
Answer in complete sentences and explain your reasoning. The student dissolved the black solid that formed by heating the copper in acid, and removed 1.8 g of copper that had not combined with oxygen. If she then added zinc to the remaining solution, what mass of copper, in grams, should be precipitated from the acidic solution?
- 5.
Answer in complete sentences and explain your reasoning. Which of the samples probably contain only one element?
- 6.
Answer in complete sentences and explain your reasoning. Which of the samples are definitely mixtures?
- 7.
What was the overall point of the copper labs (the ones we spent almost two weeks on!)? Use complete sentences with ample explanation.
- 8.
Historically speaking (and in general terms), how did scientists discover which substances on Earth were elements? Use complete sentences that explain your responses.
- 9.
If elements are the building blocks of all matter on Earth (including every living and non-living thing), why don’t we see them around us in their pure forms more often? (Use complete sentences and specific evidence to back up your responses.)
- 10.
What type of matter are you? A mixture, compound, or element? Explain. Use complete sentences with specific evidence to back up your responses
- 11.
When water is decomposed by electrolysis, the ratio of the volume of hydrogen produced to the volume of oxygen produced
- A.
Depends on how long the apparatus is connected to the power supply
- B.
Depends on the temperature of the classroom
- C.
Depends on how much water is used in the apparatus
- D.
Does not depend on any of the above because water is a compound
- E.
Depends on the temperature of the water
Correct Answer
D. Does not depend on any of the above because water is a compoundExplanation
The correct answer is that the ratio of the volume of hydrogen produced to the volume of oxygen produced does not depend on any of the above because water is a compound. This is because water is made up of two hydrogen atoms and one oxygen atom, so the ratio of their volumes produced during electrolysis is always 2:1, regardless of factors such as the duration of electrolysis, temperature, or amount of water used.Rate this question:
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- 12.
We electrolyze water and obtain 20 cm3 of hydrogen and 20 cm3 of oxygen. We mix these gases together and add a spark. What do you predict will happen?
- A.
Nothing, since the amounts of hydrogen and oxygen are not equal.
- B.
The hydrogen and oxygen will decompose into smaller substances.
- C.
The gases will react to form water, but there will be 10 cm3 of hydrogen left.
- D.
The gases will react to form water, but there will be 10 cm3 of oxygen left.
- E.
The gases will react completely to form water.
Correct Answer
D. The gases will react to form water, but there will be 10 cm3 of oxygen left.Explanation
When hydrogen and oxygen are mixed together and a spark is added, they react to form water through a chemical reaction called combustion. However, in this case, the amounts of hydrogen and oxygen are not equal. According to the balanced chemical equation for the reaction, 2 molecules of hydrogen combine with 1 molecule of oxygen to form 2 molecules of water. Therefore, if there is an excess of oxygen (10 cm3), it will be left over after the reaction is complete, while all the hydrogen will be used up to form water.Rate this question:
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- 13.
Baking soda is a white powdery substance that has a lot of uses: cleaning, baking, deodorizing. It’s a pure substance, but which of the following observations shows that baking soda is not an element?
- A.
It is a uniform white powder.
- B.
It loses mass when heated, giving off a gas in the process.
- C.
It has a density of 2.20 g/cm3.
- D.
It tastes nasty.
- E.
Some people put it in their refrigerator to absorb odors.
Correct Answer
B. It loses mass when heated, giving off a gas in the process.Explanation
The observation that baking soda loses mass when heated and gives off a gas indicates that it is not an element. Elements are pure substances that cannot be broken down into simpler substances by chemical reactions. When baking soda loses mass and releases a gas, it is undergoing a chemical reaction, suggesting that it is a compound rather than an element.Rate this question:
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- 14.
A sample of material was broken down into two substances. If getting the original substance back requires a chemical reaction, we can correctly conclude that the original material was probably
- A.
A solute
- B.
A mixture
- C.
An element
- D.
A compound
- E.
A fixed ratio
Correct Answer
D. A compoundExplanation
If getting the original substance back requires a chemical reaction, it implies that the original material underwent a chemical change. Compounds are substances that are formed when two or more elements chemically combine, resulting in a new substance with different properties. Therefore, if a chemical reaction is required to obtain the original substance, it suggests that the original material was most likely a compound.Rate this question:
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.JPG "Answer in complete sentences and explain your reasoning for credit.
10cm3 of hydrochloric acid were poured into eight evaporating dishes. Different amounts of Zinc were added to each dish and left until the reaction stopped. Each solution was then evaporated to dryness, and the mass of the residue (zinc chloride) was determined. Class data were graphed as shown below. If 6.0 g of zinc had been used in the experiment, what would be the mass of zinc chloride formed?")
.JPG "Answer in complete sentences and explain your reasoning.
Which of the samples probably contain only one element?")
.JPG "Answer in complete sentences and explain your reasoning.
Which of the samples are definitely mixtures?")
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Mar 24, 2023Quiz Edited by
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Mar 10, 2014Quiz Created by
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