C2 Essential Questions Atomic Structure Q1.This question is about atomic structure and elements.

(a) Complete the sentences.

(i) The atomic number of an atom is the number of .................................................................. (1)

(ii) The mass number of an atom is the number of .................................................................... (1)

(b) Explain why an atom has no overall charge. Use the relative electrical charges of sub-atomic particles in your explanation.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(c) Explain why fluorine and chlorine are in the same group of the periodic table. Give the electronic structures of fluorine and chlorine in your explanation.

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(d) When elements react, their atoms join with other atoms to form compounds. Complete the sentences.

Compounds formed when non-metals react with metals consist of particles called ............................. (1)

Compounds formed from only non-metals consist of particles called ……........................................ . (1)

(e) Two isotopes of oxygen are oxygen-16 and oxygen-18.

16 18

O O 8 8

oxygen-16 oxygen-18

Explain, in terms of particles, how the nucleus of an oxygen-18 atom is different from the nucleus of an oxygen-16 atom.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(Total 10 marks)

Chemical Reactions

Sodium oxide contains sodium ions (Na+) and oxide ions (O2–).

Describe, in terms of electrons, what happens when sodium atoms reacts with an oxygen atom to produce

sodium oxide.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (4)

GC-MS

What does GC-MS stand for? .....................................................................................................................

Use the diagram to bullet point the important steps in doing GC-MS

- GC

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

- MS

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (5)

(c) The following chromatogram was obtained when a mixture was separated.

Identify:

- The substance with the shortest retention time ………..

- The substance with the highest molecular mass ………..

- The substance there is most of in the mixture ………..

- The number of compounds in the mixture ………..

- (4) - (Total 9 marks)

Metallic Bonding

Q3. High quality SCART leads are used to connect a satellite box to a television. The connectors should conduct electricity very well and should not corrode. The connectors are often coated with gold.

(a) Gold is a typical metal. Describe the structure and bonding of gold.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (3)

(ii) Why is gold a good conductor of electricity?

......................................................................................................................................................................

...................................................................................................................................................................... (1)

(iii) 18-carat gold has been mixed with 2 other metals and is only 75% pure. 18 carat gold is harder than pure gold. Explain why.

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(Total 6 marks)

Ionic Bonding

Q2.. (a) Magnesium iodide is an ionic compound. It contains magnesium ions (Mg2+

) and iodide ions

(I─) Describe, in terms of electrons, what happens when magnesium reacts with iodine.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (4)

(b) The diagram shows the structure of potassium iodide.

Explain why a high temperature is needed to melt potassium iodide.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

Solid potassium iodide does not conduct electricity. Why does potassium iodide solution conduct electricity?

......................................................................................................................................................................

...................................................................................................................................................................... (1)

(Total 8 marks)

Simple Covalent Bonding

Q4. Ammonia has the formula NH3

The diagrams show how electrons are arranged in nitrogen and hydrogen atoms.

(a) Draw a diagram to show how the electrons are arranged in an ammonia molecule.

You need only show the electrons in the highest energy level.

(2)

(b) Ammonia is a gas at room temperature. Explain why ammonia has a low boiling point.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(c) Explain, in terms of particles, why liquid iodine does not conduct electricity.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(Total 6 marks)

Giant Covalent Bonding

Q5.The diagrams show the structures of diamond and graphite.

Diamond Graphite

(a) Diamond and graphite both contain the same element.

What is the name of this element? ............................................................... (1)

(b) Use the diagrams above and your knowledge of structure and bonding to explain why:

(i) graphite is very soft

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

.............................................................................................................................................. (2)

(ii) diamond is very hard

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

.............................................................................................................................................. (2)

(iii) graphite conducts electricity

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

.............................................................................................................................................. (2)

(Total 7 marks)

Calculations

Q6. Metal compounds have been used for thousands of years as colours in paint.

One compound used is magnesium oxide.

(a) (i) Calculate the relative formula mass (Mr) of magnesium oxide.

Relative atomic masses: O = 16; Mg = 24.

......................................................................................................................................................................

......................................................................................................................................................................

Relative formula mass = ..................................... (2)

(ii) Calculate the percentage by mass of magnesium in magnesium oxide.

......................................................................................................................................................................

......................................................................................................................................................................

Percentage by mass of magnesium in magnesium oxide = .............% (2)

(iii) Calculate the mass of magnesium needed to make 25 g of magnesium oxide.

..............................................................................................................

Mass of magnesium = ..................................... g (1)

(b) A sample of a red oxide used in paint was found to contain 6.21 g of lead and 0.64 g of oxygen.

Calculate the empirical (simplest) formula of this compound.

You must show all your working to gain full marks.

Relative atomic masses: O = 16; Pb = 207.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (4)

(Total 9 marks)

Rates of Reaction

Q7 (a) A student performed an experiment reacting samples of limestone with hydrochloric acid.

CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)

In one experiment he used powdered marble; in the other he used marble chips.

The rate of reaction between the marble and hydrochloric acid particles was much faster with the powder. Explain why.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(b) The student repeated the experiments, increasing the temperature from 20°C to 40°C.

‘the rate of reaction increases when the temperature is increased’.

Explain, in terms of particles, why the rate of reaction increases.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(c) The student repeated the original experiments, decreasing the concentration of the hydrochloric acid. Explain, in terms of particles, why the rate of reaction decreases.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(d) The mass of the flask and contents decreased during the experiment. Use the equation for this reaction to help you explain why.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(Total 8 marks)

Electrolysis

Q8. Zinc is produced by electrolysis of molten zinc chloride, as shown in the figure below.

(a) (i) Why must the zinc chloride be molten for electrolysis?

...................................................................................................................................................................... (1)

(ii) Describe what happens at the negative electrode.

......................................................................................................................................................................

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (3)

(b) When sodium chloride solution is electrolysed, one product is chlorine.

Name the two other products from the electrolysis of sodium chloride solution.

...................................................................................................................................................................... (2)

(c) Aluminium is extracted from aluminium oxide using electrolysis. The diagram shows a cell used for the extraction of aluminium.

(i) The electrolyte contains cryolite. Explain why.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(ii) The positive electrode in the cell is used up during the process. Explain why.

......................................................................................................................................................................

......................................................................................................................................................................

...................................................................................................................................................................... (2)

(Total 8 marks)

Reversible Reactions and Acids, Bases and Salts

In a chemical equation, what do the following abbreviations mean?

(s) …………………………….. (l) ………………………….. (g) ………………………… (aq) ……………………………..

(4)

Which technique allows soluble salts to be isolated from solution? ……………………..……………………………..

An insoluble solid formed when to solutions are mixed is called a ……………………………………………..……..

This technique is useful when ………………………………………………………………………….

Which technique allows insoluble salts to be isolated from a mixture? … ……………………..……………………………..

(4)

Which ion is found in all acids? ………………….. Which ion is found in all alkalis? …………………..

An alkali is a soluble ………………….

Write and equation to show what happens when an acid reacts with an alkali:

……………………..…………………………….……………………..…………………………….……………………..…………………………….………………….

This type of reaction is called: …………………………………………………………………

After this reaction, the pH of the mixture will be ………………………..

(5)

When ammonia is dissolved in water it produces hydroxide ions and …………………………………….. ions.

These are used in the manufacture of ……………………………………….

(2)

When hydrochloric acid reacts, it salts are called ……………………………..

When sulphuric acid reacts, it salts are called ……………………………..

When nitric acid reacts, it salts are called ……………………………..

(3)

A reaction that gives out heat energy is …………………………….. Example …………………………………….…………

A reaction that takes in heat energy is …………………………….. Example ……………………………………..…………

(4)

Copper sulphate that contains water inside the crystals is said to be …………………………………….………….

Copper sulphate that contains no water inside the crystals is said to be …………………………………….………….

Describe the colour change as the top one is heated to form the bottom one …………………………………….…………

(3) (25 marks)

More Calculations

Relative atomic masses: Titanium – 48 Magnesium – 24 Chlorine – 35.5

TiCl4 + Mg Ti + MgCl2

1. Balance the equation (2 marks)

2. Calculate the relative molecular mass (Mr) for each of these compounds (2 marks):

TiCl4

MgCl2

3. Calculate the percentage chlorine by mass for each of these compounds (2 marks):

TiCl4

MgCl2

4. Another compound of titanium contains 40.34% titanium and 59.66% chlorine. Determine the

empirical formula (4 marks):

Ti Cl

Percentage/Mass

Relative atomic mass

Result from Step 1

Lowest result from Step 1

Empirical formula =

5. If you start off with 31.67g of TiCl4, what mass of titanium would be produced? (3 marks)

6. Instead of getting this amount, a student only obtained 7.2g of titanium. Calculate the percentage

yield (1 mark):

[If you do not have an answer to 5, assume the expected mass of titanium to be 12g]

Relative atomic masses: Copper – 63.5 Sulphur – 32 Oxygen – 16 Hydrogen - 1

CuO + H2SO4 CuSO4 + H2O

1. Balance the equation (2 marks)

2. Calculate the relative molecular mass (Mr) for each of these compounds (3 marks):

CuO

H2SO4 CuSO4 H2O

3. Calculate the percentage oxygen by mass for each of these compounds (3 marks):

CuO

H2SO4 CuSO4 H2O

4. Another compound of copper contains 88.8% copper and 11.2% oxygen. Determine the empirical

formula (4 marks):

Cu O

Percentage/Mass

Relative atomic mass

Result from Step 1

Lowest result from Step 1

Empirical formula =

5. If you start off with 15.9g of CuO, what mass of copper sulphate would be produced? (3 marks)

6. Instead of getting this amount, a student only obtained 3.2g of copper sulphate. Calculate the

percentage yield (1 mark):

[If you do not have an answer to 5, assume the expected mass of copper oxide to be 34g]