Types of Chemical Reactions: Quiz

Question 1EasyWhat type of reaction is 2H₂O₂ → 2H₂O + O₂?

SynthesisDecompositionSingle displacementDouble displacement

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Answer: Decomposition

One compound breaks into two simpler substances: decomposition.

Question 2EasyWhat type of reaction is Mg + 2HCl → MgCl₂ + H₂?

SynthesisDecompositionSingle displacementCombustion

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Answer: Single displacement

An element (Mg) replaces hydrogen in a compound: single displacement. Magnesium is above hydrogen in the activity series.

Question 3EasyWhat are the products of the complete combustion of ethanol, C₂H₅OH?

CO and H₂CO₂ and H₂OC and H₂OCO₂ and H₂

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Answer: CO₂ and H₂O

Complete combustion of a compound of C, H and O gives carbon dioxide and water: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O.

Question 4MediumWhich metal will displace copper from copper(II) sulfate solution?

SilverGoldIronNone of these

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Answer: Iron

Iron is above copper in the activity series: Fe + CuSO₄ → FeSO₄ + Cu. Silver and gold are below copper.

Question 5MediumWhich halogen reaction takes place?

I₂ + 2KCl → 2KI + Cl₂Br₂ + 2KCl → 2KBr + Cl₂Cl₂ + 2KI → 2KCl + I₂I₂ + 2KBr → 2KI + Br₂

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Answer: Cl₂ + 2KI → 2KCl + I₂

A more reactive halogen displaces a less reactive one (F > Cl > Br > I). Only chlorine displacing iodine fits.

Question 6MediumWhy do KNO₃(aq) and NaCl(aq) not react when mixed?

They are both solidsNo precipitate, water or gas can formPotassium is too reactiveThey form a precipitate of KCl

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Answer: No precipitate, water or gas can form

The possible products KCl and NaNO₃ are both soluble, so the ions stay in solution and there is no reaction.

Question 7HardWhat mass of CO₂ is released when 10.0 g of CaCO₃ (100.09 g/mol) decomposes completely? (CO₂: 44.01 g/mol)

2.27 g4.40 g5.60 g10.0 g

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Answer: 4.40 g

10.0 g ÷ 100.09 g/mol = 0.0999 mol CaCO₃ = 0.0999 mol CO₂; × 44.01 g/mol = 4.40 g. 5.60 g is the mass of CaO formed.