Question 5

Study the physical and chemical processes below and answer the questions that
follow.

X: H₂O(s) → H₂O(g)
Y: CaCO₃(s) ∆ → CaO(s) + CO₂(g)
Z: Iron + Oxygen → Iron(III) oxide

5.1 Define the term physical change. (2)

5.2 Write down the LETTER of the process that represents the following:

5.2.1 Physical change (1)

5.2.2 Decomposition reaction (1)

5.3 Give the name of the physical change stated in QUESTION 5.2.1. (1)

5.4 State TWO properties of a reaction that indicate that a chemical change has
taken place. (2)

5.5 For process Z, write down:

5.5.1 What the symbol ∆ represents (1)

5.5.2 A BALANCED CHEMICAL EQUATION (Show the phases of ALL
reactants and products.) (4)

5.6 A 20 g sample of CaCO₃(s) in process Y decomposes to form 11,2 g of CaO.
In a second sample, 30 g decomposes to form x g of CO₂.

5.6.1 State the law of constant composition. (2)

5.6.2 Use the law in QUESTION 5.6.1 to calculate mass 𝑥 of the
CO₂ formed. (4)

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