Classify reactions: synthesis, decomposition, replacement, combustion

Answer Key - Grade 10 Science Worksheet - Building Confidence

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

1. 1.

   100 g of calcium carbonate decomposes on heating into 56 g of calcium oxide and some carbon dioxide gas. What mass of carbon dioxide forms, Ari?

   44 g
2. 2.

   18 g of water decomposes with electricity into 2 g of hydrogen gas and some oxygen gas. What mass of oxygen forms, Bo?

   16 g

3. Read this first

   Five reaction types (textbook patterns)

   type	pattern	example
   synthesis	A + B → AB	2 Na + Cl₂ → 2 NaCl
   decomposition	AB → A + B	CaCO₃ → CaO + CO₂
   single replacement	A + BC → AC + B	Zn + 2 HCl → ZnCl₂ + H₂
   double replacement	AB + CD → AD + CB	AgNO₃ + NaCl → AgCl + NaNO₃
   combustion	fuel + O₂ → CO₂ + H₂O	CH₄ + 2 O₂ → CO₂ + 2 H₂O

4. 3.

   Using the card, which pattern shows one reactant splitting into two products, Jun?

   • AB → A + B
   • A + B → AB
   • A + BC → AC + B
5. 4.

   Using the card, which type has two compounds trading partners, Kira?

   • Single replacement
   • Synthesis
   • Double replacement
6. 5.

   Using the card, what does a fuel like methane make when it burns completely, Luz?

   • CO₂ and H₂O
   • C and H₂
   • CH₄ and O₂
7. 6.

   What type of reaction is CaCO₃ → CaO + CO₂, Noah?

   • Synthesis
   • Decomposition
   • Single replacement
8. 7.

   What type of reaction is Zn + 2 HCl → ZnCl₂ + H₂, Pia?

   • Single replacement
   • Synthesis
   • Double replacement
9. 8.

   What happens in a synthesis reaction, Ren?

   • Two compounds trade partners
   • Substances join into one product
   • One compound splits apart
10. 9.

    Which reaction type always has oxygen gas as a reactant, Tala?

    • Decomposition
    • Combustion
    • Double replacement
11. 10.

    How many reactants does a decomposition reaction start with, Zee?

    • Two compounds
    • Two elements
    • Just one compound