Chemical Composition: Problem Set
Name____________________________________
1. Using large circles for oxygen atoms and small circles for hydrogen atoms illustrate the
balanced chemical reaction when oxygen gas reacts with hydrogen gas to form water.
2. Using large circles for oxygen atoms and small circles for hydrogen atoms illustrate the
balanced chemical reaction when hydrogen peroxide decomposes to form oxygen gas and
water.
3. 18 mL of oxygen gas is mixed with 10 mL of hydrogen gas in a test tube. A spark is generated
inside the tube to allow the two gases to react to form water. Identify the gas that remains (if any)
and how much of it is still present in the test tube.
4. In lab you tested for three gases, each of which produced specific results that constitute the
presence of the gas. Identify the type of splint and the observations for the identification of the
gas.
Gas
Splint
Observations
Oxygen
Hydrogen
Carbon dioxide
5. When water is boiling, what is inside the bubbles? During the electrolysis of water, what’s
inside the bubbles? Why do each of these processes produce different results?
6. Indicate which of the following represent a physical change (P) and which represents a
chemical change (C).
_____ tearing a sheet of paper
_____ burning a candle
_____ using a battery to light a bulb
_____ boiling water
_____ chewing a candy bar
_____ digesting a candy bar