N5 Chemistry MC 2015

An atom has 26 protons, 26 electrons and 30 neutrons.

The atom has

• atomic number 26, mass number 56

• atomic number 56, mass number 30

• atomic number 30, mass number 26

• atomic number 52, mass number 56

Answer explanation

Atomic number = number of protons

Mass number = protons + neutrons

The table shows the numbers of protons, electrons and neutrons in four particles,

W, X, Y and Z. Which pair of particles are isotopes?

• W and X

• W and Y

• X and Y

• Y and Z

Answer explanation

Isotope = same number of protons, different number of neutrons

Which of the following particles contains a different number of electrons from the others?

You may wish to use the data booklet to help you.

• Cl^—

• S^2—

• Ar

• Na⁺

Answer explanation

A Cl^- ions have an electron arrangement of 2,8,8

B S^2- ions have an electron arrangement of 2,8,8

C Ar atoms have an electron arrangement of 2,8,8

D Na⁺ ions have an electron arrangement of 2,8

Which of the following diagrams shows the apparatus which would allow a soluble gas to be

removed from a mixture of gases?

• 
• 
• 
• 

Answer explanation

A Gas would not need to pass through water to escape

B Gas would not pass through water (test tube would explode as pressure builds)

C Gas passes through water and escapes test tube through tube at top

D Gas would pass through water but test tube would explode as pressure builds

Which of the following diagrams could be used to represent the structure of a covalent

network?

• 
• 
• 
• 

Answer explanation

A = Metallic Lattice

B = Ionic Lattice

C = Covalent Molecule

D = Covalent Network

What is the charge on the chromium ion in CrCl₃?

• 1+

• 1-

• 3+

• 3-

Answer explanation

Balance the charge: 3 x Cl = 3-

Cr = 3+

The table contains information about calcium and calcium chloride. When molten calcium chloride is electrolysed at 800 ºC the calcium appears as a

• solid at the bottom of the molten calcium chloride

• liquid at the bottom of the molten calcium chloride

• solid on the surface of the molten calcium chloride

• liquid on the surface of the molten calcium chloride

Answer explanation

Solid calcium (not yet melted at 800^oC) is less dense than molten calcium chloride (it has melted at 800^oC)

x Al(s) + yBr₂(l) → z AlBr₃(s)

This equation will be balanced when

• x = 1, y = 2 and z = 1

• x = 2, y = 3 and z = 2

• x = 3, y = 2 and z = 3

• x = 4, y = 3 and z = 4

Answer explanation

2Al(s) + 3Br₂(l) --> 2AlBr₃(s)

0∙2 mol of a gas has a mass of 12∙8 g.

Which of the following could be the molecular formula for the gas?

• SO₂

• CO

• CO₂

• NH₃

Answer explanation

A gfm SO₂ = (1x32)+(2x16) = 32+32 =64g - mass = n x gfm = 0.2 x 64 = 12.8g

B 1mol CO = (1x12)+(1x16) = 12+16 =28g - mass = n x gfm = 0.2 x 28 = 5.6g

C 1mol CO₂ = (1x12)+(2x16) = 12+32 =44g - mass = n x gfm = 0.2 x 44 = 8.8g

D 1mol NH₃ = (1x14)+(3x1) = 14+1 =17g - mass = n x gfm = 0.2 x 17 = 3.4g

Which of the following oxides, when shaken with water, would leave the pH unchanged?

You may wish to use the data booklet to help you.

• Carbon dioxide

• Copper oxide

• Sodium oxide

• Sulfur dioxide

Answer explanation

Copper oxide is insoluble in water