# Chapter Six Test: Compounds And Elements

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### 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

D. Does not depend on any of the above because water is a compound
Explanation
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.

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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.

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.

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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.

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Some people put it in their refrigerator to absorb odors.

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.

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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

D. A compound
Explanation
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.

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• Current Version
• Mar 24, 2023
Quiz Edited by
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• Mar 10, 2014
Quiz Created by
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