Chemistry: High School: 9th and 10th Grade Quiz - Balancing Symbol Equations (Questions)

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Chemistry is all about chemical reactions. Scientists find equations, using either words or symbols, a handy tool to help them understand exactly what is going on in chemical reactions. Balancing these equations is a vital skill for any drugstore and necessary for a high grade in high school Chemistry. This quiz will test students’ understanding and knowledge when faced with balancing symbol equations.

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In chemistry, equations show what is happening in a chemical reaction. The starting materials are known as the reactants (sometimes called reagents) and the new materials are called the products. Scientists use balanced symbol equations in order to describe chemical reactions. Calculations of reacting quantities can be made using these balanced equations so they are of great importance to anyone involved with chemistry. At first, balancing symbol equations can seem daunting but if you follow a few simple rules, it becomes a lot easier!

At high school, it is best to begin with a word equation so that you can quickly see that you have all of the reactants and products. Underneath that, write down the correct formula for each of the chemicals. This is the crucial step - if any of the formulae are wrong, the final equation may never balance. Once that is done, you can count the atoms of the individual elements on both sides of the reaction. Make two lists on a piece of rough paper, one for the atoms on the reagents side and another for the products. The Law of Conservation of Matter means that the products must contain exactly the same number and type of atoms as the reactants, but not joined together in the same way. When the two lists contain exactly the same numbers and types of atoms, the equation is balanced.

You can then start to balance the equation. Some equations will automatically be balanced but the majority won't be. You cannot change the formulae (unless you realize one of them is wrong), all you can do is to change the quantities of each formula. You do this by placing a number in front of the formulae as required e.g. 2NaCl or 3H2O. This doubles, trebles, quadruples etc. ALL of the elements in the formula. NaCl means that you have one atom of sodium and one of chlorine. Placing a 2 in front doubles the numbers of both the sodium and chlorine atoms. This works with every formula. As you add a number, you need to update your lists of atoms.

Balancing symbol equations, which is only required on the higher tier paper, is much harder to describe than it is to do! Practice makes perfect so try your hand at this quiz and sharpen your equation balancing skills!

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1. Choose the correctly balanced chemical equation from the list.
[ ] CH4 + 2O2 → CO2 + H2O
[ ] CH4 + 3O2 → CO2 + 2 H2O
[ ] CH4 + 2O2 → CO2 + 2 H2O
[ ] CH4 + 2O2 → CO2 + 3 H2O
2. Choose the correctly balanced chemical equation from the list.
[ ] FeO3 + 3CO → Fe + 3CO2
[ ] 2FeO3 + 2CO → Fe + 3CO2
[ ] FeO3 + 3CO → Fe + 2CO2
[ ] FeO3+ 3CO → Fe + CO2
3. Choose the correctly balanced chemical equation from the list.
[ ] 2H2 SO4 + Pb(OH)4 → Pb(SO4)2 + 4H2O
[ ] H2 SO4 + Pb(OH)4 → Pb(SO4)2 + 4H2O
[ ] 2H2 SO4 + Pb(OH)4 → PbSO4 + 4H2O
[ ] 2H2 SO4 + Pb(OH)4 → Pb(SO4)2 + H2O
4. Choose the correctly balanced chemical equation from the list.
[ ] Al + 6HCl → 2AlCl3 + 3H2
[ ] 2Al + 6HCl → 2AlCl3 + 3H2
[ ] Al + HCl → AlCl3 + H2
[ ] 2Al + HCl → AlCl3 + 3H2
5. Choose the correctly balanced chemical equation from the list.
[ ] 3Na3PO4 + 3HCl → 3NaCl + H3PO4
[ ] Na3PO4 + 2HCl → 3NaCl + H3PO4
[ ] Na3PO4 + HCl → NaCl + H3PO4
[ ] Na3PO4 + 3HCl → 3NaCl + H3PO4
6. Choose the correctly balanced chemical equation from the list.
[ ] Mg(OH)2 + 2HCl → MgCl2 + H2O
[ ] Mg(OH)2 + 2HCl → MgCl2 + 2H2O
[ ] Mg(OH)2 + HCl → MgCl2 + H2O
[ ] MgOH + 2HCl → MgCl2 + 2H2O
7. Choose the correctly balanced chemical equation from the list.
[ ] TiCl4 + H2O → TiO + 4HCl
[ ] TiCl4 + 3H2 → TiO2 + 5HCl
[ ] TiCl4 + H2 → TiO2 + HCl
[ ] TiCl4 +2H2O → TiO2 + 4HCl
8. Choose the correctly balanced chemical equation from the list.
[ ] 2NaBr + Cl2 → 2NaCl + Br2
[ ] NaBr + Cl2 → NaCl + Br2
[ ] 2NaBr + Cl2 → NaCl + Br2
[ ] 3NaBr + Cl2 → 3NaCl + Br2
9. Choose the correctly balanced chemical equation from the list.
[ ] C2H6 + 31/2O2 → 2CO2 + 3H2O
[ ] C2H6 + 7O2 → 4CO2 + 5H2O
[ ] C2H6 + 3O2 → 2CO2 + 3H2O
[ ] C2H6 + 31/2O2 → CO2 + 3H2O
10. Choose the correctly balanced chemical equation from the list.
[ ] PCl5 + H2O → H3PO4 + HCl
[ ] PCl5 + 4H2O → H3PO4 + HCl
[ ] PCl5 + 4H2O → H3PO4 + 5HCl
[ ] PCl5 + 4H2O → H3PO4 + 5HC
Chemistry: High School: 9th and 10th Grade Quiz - Balancing Symbol Equations (Answers)
1. Choose the correctly balanced chemical equation from the list.
[ ] CH4 + 2O2 → CO2 + H2O
[ ] CH4 + 3O2 → CO2 + 2 H2O
[x] CH4 + 2O2 → CO2 + 2 H2O
[ ] CH4 + 2O2 → CO2 + 3 H2O
The complete combustion of methane
2. Choose the correctly balanced chemical equation from the list.
[x] FeO3 + 3CO → Fe + 3CO2
[ ] 2FeO3 + 2CO → Fe + 3CO2
[ ] FeO3 + 3CO → Fe + 2CO2
[ ] FeO3+ 3CO → Fe + CO2
One Fe, three C and six O atoms on each side
3. Choose the correctly balanced chemical equation from the list.
[x] 2H2 SO4 + Pb(OH)4 → Pb(SO4)2 + 4H2O
[ ] H2 SO4 + Pb(OH)4 → Pb(SO4)2 + 4H2O
[ ] 2H2 SO4 + Pb(OH)4 → PbSO4 + 4H2O
[ ] 2H2 SO4 + Pb(OH)4 → Pb(SO4)2 + H2O
Remember, brackets in chemistry work the same as in math
4. Choose the correctly balanced chemical equation from the list.
[ ] Al + 6HCl → 2AlCl3 + 3H2
[x] 2Al + 6HCl → 2AlCl3 + 3H2
[ ] Al + HCl → AlCl3 + H2
[ ] 2Al + HCl → AlCl3 + 3H2
Two Al, six H and six Cl on each side
5. Choose the correctly balanced chemical equation from the list.
[ ] 3Na3PO4 + 3HCl → 3NaCl + H3PO4
[ ] Na3PO4 + 2HCl → 3NaCl + H3PO4
[ ] Na3PO4 + HCl → NaCl + H3PO4
[x] Na3PO4 + 3HCl → 3NaCl + H3PO4
This one looks worse than it is - all that happens is that the Na and the H swap places during the reaction
6. Choose the correctly balanced chemical equation from the list.
[ ] Mg(OH)2 + 2HCl → MgCl2 + H2O
[x] Mg(OH)2 + 2HCl → MgCl2 + 2H2O
[ ] Mg(OH)2 + HCl → MgCl2 + H2O
[ ] MgOH + 2HCl → MgCl2 + 2H2O
Balancing equations gets easier the more you do
7. Choose the correctly balanced chemical equation from the list.
[ ] TiCl4 + H2O → TiO + 4HCl
[ ] TiCl4 + 3H2 → TiO2 + 5HCl
[ ] TiCl4 + H2 → TiO2 + HCl
[x] TiCl4 +2H2O → TiO2 + 4HCl
Titanium oxide is used in sun creams
8. Choose the correctly balanced chemical equation from the list.
[x] 2NaBr + Cl2 → 2NaCl + Br2
[ ] NaBr + Cl2 → NaCl + Br2
[ ] 2NaBr + Cl2 → NaCl + Br2
[ ] 3NaBr + Cl2 → 3NaCl + Br2
One of the halogen displacement reactions
9. Choose the correctly balanced chemical equation from the list.
[x] C2H6 + 31/2O2 → 2CO2 + 3H2O
[ ] C2H6 + 7O2 → 4CO2 + 5H2O
[ ] C2H6 + 3O2 → 2CO2 + 3H2O
[ ] C2H6 + 31/2O2 → CO2 + 3H2O
It is more common to use integers (whole numbers) for balancing equations but you will sometimes see equations that have been balanced in this way using 1/2
10. Choose the correctly balanced chemical equation from the list.
[ ] PCl5 + H2O → H3PO4 + HCl
[ ] PCl5 + 4H2O → H3PO4 + HCl
[x] PCl5 + 4H2O → H3PO4 + 5HCl
[ ] PCl5 + 4H2O → H3PO4 + 5HC
The reaction of phosphorous pentachloride with water is very violent!