Balance chemical equations

Answer Key - Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   In 3 Ca(NO₃)₂, the coefficient is 3, there are 2 nitrate groups per unit and 3 oxygens per nitrate. How many oxygen atoms in all, Ari?

   18 atoms
2. 2.

   In 2 Al₂(SO₄)₃, the coefficient is 2, there are 3 sulfate groups per unit and 4 oxygens per sulfate. How many oxygen atoms in all, Bo?

   24 atoms
3. 3.

   In 3 (NH₄)₂CO₃, the coefficient is 3, there are 2 ammonium groups per unit and 4 hydrogens per ammonium. How many hydrogen atoms in all, Esme?

   24 atoms
4. 4.

   Which coefficients balance Mg + O₂ → MgO, Jun?

   • 2, 1, 2
   • 1, 1, 1
   • 1, 2, 2
5. 5.

   Which coefficients balance Na + Cl₂ → NaCl, Kira?

   • 2, 1, 2
   • 2, 2, 1
   • 1, 2, 1
6. 6.

   Which coefficients balance Al + O₂ → Al₂O₃, Luz?

   • 2, 3, 1
   • 4, 3, 2
   • 2, 1, 1
7. 7.

   In CaCO₃ → CaO + CO₂, why can't carbonate be counted as a unit, Milo?

   • Carbonate has no charge
   • Calcium is a polyatomic ion here
   • It breaks apart into CaO and CO₂
8. 8.

   When should a polyatomic ion be balanced as one unit, Noah?

   • When it is the first formula in the equation
   • When it has oxygen in it
   • When it appears unchanged on both sides
9. 9.

   Why balance a polyatomic ion as one unit when it stays whole, Pia?

   • It saves counting each atom
   • It changes the ion's overall charge
   • It adds atoms
10. 10.

    In a word equation, how is the element oxygen written, Zee?

    • O₂
    • O
    • O₃