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Edexcel IGCSE Chemistry E Chemical Formulae Equations and Calculations Questions

Practise balancing equations and using formulae, Mr and mole ratios for reacting masses, yields and composition.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • balance formula units and state symbols before taking stoichiometric ratios
  • convert between mass and moles using Mr, then apply the balanced-equation ratio
  • calculate percentage composition, yield or empirical formula from supplied data

Covered syllabus points

1.25 Chemical equations1.26 Relative formula mass1.27 The mole1.28 Amount of substance calculations1.29 Reacting masses1.30 Percentage yield1.31 Experimental formulae1.32 Empirical and molecular formulae1.33 Formula calculations1.34C Solution concentration calculations1.35C Gas volume calculations1.36 Metal oxide formula practical

Question 1

[Maximum number: 5]

This question is about magnesium metal and its compounds.

Question (a)

(a)

Magnesium burns in oxygen gas to form solid magnesium oxide.

[ 2 ]

Question (i)

(i)

Complete the chemical equation for the reaction by balancing the equation and adding the state symbols.

Figure for Question (i) — Edexcel IGCSE Chemistry
[ 2 ]

Question (b)

(b)

A student uses this method to make a solution of magnesium chloride.

Step 1. measure 25 cm325 \mathrm{~cm}^{3} of dilute hydrochloric acid into a beaker
Step 2 add magnesium powder a little at a time
Step 3 keep adding magnesium powder until it is in excess
Step 4 remove the excess magnesium powder by filtration

This is the equation for the reaction.

Figure for Question (b) — Edexcel IGCSE Chemistry
[ 3 ]

Question (i)

(i)

Calculate the minimum mass of magnesium needed to react with 25.0 cm325.0 \mathrm{~cm}^{3} of 2.00 mol/dm32.00 \mathrm{~mol} / \mathrm{dm}^{3} hydrochloric acid.
[for Mg,Ar=24\mathrm{Mg}, \mathrm{A}_{\mathrm{r}}=24 ]

mass = g

[ 3 ]

Question 2

[Maximum number: 1]

Crude oil is a mixture of hydrocarbons.

One of the hydrocarbons in the refinery gas fraction is an alkane with the structural formula CH3CH2CH2CH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}

Calculate the relative molecular mass (Mr)\left(M_{\mathrm{r}}\right) of this alkane.

Mr=M_{r}=

Question 3

[Maximum number: 3]

The diagram shows the positions of some elements in part of the Periodic Table.

Na Al S Cl
K Xe
In

Table for Question 3 — Edexcel IGCSE Chemistry

A teacher adds a small piece of sodium to a glass trough containing water and universal indicator.

The universal indicator changes colour.
The equation for the reaction is

2Na( s)+2H2O(l)→2NaOH(aq)+H2( g)2 \mathrm{Na}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})

The reaction with sodium produces 0.036 g of hydrogen gas.

One mole of hydrogen gas contains 6.0×10236.0 \times 10^{23} molecules.
Calculate the number of molecules of hydrogen gas produced in the reaction with sodium.

Give your answer to two significant figures.
number of molecules of hydrogen gas =

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