Chemistry GCSE

Revision Questions

What name is given to a reaction which gives out heat?

Exothermic (endothermic reactions take in

heat)

What is an igneous rock?

Igneous rock is formed from solidified magma (molten rock).

Describe a test for alkenes.

Alkenes decolourise bromine water

What two elements form ammonia?

nitrogen and hydrogen.

What type of reaction is characterised by the gain of

electrons?

reductionoxidation is the loss of electrons.

Ma

ss in g

0.6

0.5

0.4

0.3

0.2

0.1

0

0 1 2 3 4 5 6

Time in minutes

A student studied the reaction between dilute hydrochloric acid and an excess of copper carbonate:copper carbonate + hydrochloric acid copper chloride + water + carbon dioxideThe student measured the mass loss during a given time. The results are shown in the table below:

time in minutes

1 2 3 4 5 6

mass lost in g 0.24 0.42 0.49 0.53 0.54 0.54(a) Plot the mass lost against time on the grid below. (3marks)

(b) After how many minutes had all the acid been used up? .............................................. Minutes (1 mark)(c) A second experiment was carried out at a higher temperature. All other factors were the same. Draw a line on the graph above to show the results that you would expect. (2 marks)

Ma

ss in g

0 1 2 3 4 5 6

Time in minutes

A student studied the reaction between dilute hydrochloric acid and an excess of copper carbonate:copper carbonate + hydrochloric acid copper chloride + water + carbon dioxideThe student measured the mass loss during a given time. The results are shown in the table below:

time in minutes

1 2 3 4 5 6

mass lost in g 0.24 0.42 0.49 0.53 0.54 0.54(a) Plot the mass lost against time on the grid below. (3marks)

(b) After how many minutes had all the acid been used up? ........4.7.................................... Minutes (1 mark)(c) A second experiment was carried out at a higher temperature. All other factors were the same. Draw a line on the graph above to show the results that you would expect. (2 marks)

Mark each point clearly with a dot or cross. This will gain 2 marks. Draw the best fit line smoothly ignoring any anomalous points. As no mass is lost the line should go through (0,0).

The second graph must have a steeper slope but the same maximum.

Don’t forget to label your new graph.

0.6

0.5

0.4

0.3

0.2

0.1

0

Line to show higher

temperature experiment

The Ablonian 1 Drona coin is made of an alloy of zinc, silver and copper.The bar chart shows the mass of each metal in a 200g bar of this alloy..

(a) (i) Calculate the percentage of copper, in the coins........................................................................................................................................................................................................................................................ (1 mark)(ii) The Drona coin has a mass of 8 grams.Calculate the mass of copper in this coin.................................................................................................................................................................................................................................................................................Mass of copper = ........................................ g (2 marks)(b) Many metals can be extracted by removing oxygen from their ores.(i) What name is given to a reaction in which oxygen is removed from a substance?......................................................................................................................... (1 mark)(ii) Which metal in the coin cannot be extracted from its ore in this way? Explain your answer......................................................................................................................................................................................................................................................................................................................................................................................................................... (2 marks)

0

20

40

60

80

100

120

140

160

180

zinc silver copper

The Ablonian 1 Drona coin is made of an alloy of zinc, silver and copper.The bar chart shows the mass of each metal in a 200g bar of this alloy..

(a) (i) Calculate the percentage of Copper, in the coins..............160 200 x100 =80% ........................................................................... .(1 mark)(ii) The Drona coin has a mass of 8 grams.Calculate the mass of copper in this coin...............................8x80100............1 mark. .for just the working 2 marks for the correct answer........................................................................................................................................Mass of copper = ...................... 6.4 .................. g (2 marks)(b) Many metals can be extracted by removing oxygen from their ores.(i) What name is given to a reaction in which oxygen is removed from a substance?............................................... Reduction ...............................................................(1 mark)(ii) Which metal in the coin cannot be extracted from its ore in this way? Explain your answer......... Silver because silver is less reactive than carbon .................................................Remember if the question says explain you need to have a ‘because’ in your answer.......................................................................................................................... (2 marks)

0

20

40

60

80

100

120

140

160

180

zinc silver copper

(a) Name this method of separating crude oil............................................................................................................... (1 mark) (b) Crude oil contains hydrocarbon molecules of different sizes. Which of the fractions contains the largest hydrocarbon molecules?............................................................................................................. (1 mark)(c) The fuel gas fraction includes the hydrocarbon methane, CH4.

Name the group of hydrocarbons which includes methane and ethane.……………………………………………………………………………….. (1 mark)(d) More of the fuel fraction is obtained than can be used. Some of it is cracked to produce more useful products. Describe as fully as you can the process of cracking.………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….. (3 marks)

Crude oil is a mixture of many hydrocarbons. The diagram shows the method used to separate crude oil.

Heated crude oil in

fuel gaspetrol

paraffin

diesel

fuel

bitumen

naptha

(a) Name this method of separating crude oil................ fractional distillation .............................................................................. (1 mark) (b) Crude oil contains hydrocarbon molecules of different sizes. Which of the fractions contains the largest hydrocarbon molecules?................ bitumen ............................................................................................. (1 mark)(c) The fuel gas fraction includes the hydrocarbon methane, CH4.

Name the group of hydrocarbons which includes methane and ethane.……………… alkanes ……………………………………………………………….. (1 mark)(d) More of the fuel fraction is obtained than can be used. Some of it is cracked to produce more useful products. Describe as fully as you can the process of cracking.Long chain hydrocarbons can be broken into down into smaller chains (1mark) by passing the vapour over a heated catalyst (1 mark). This process is called thermal decomposition(1 mark) Alkenes/c=c/double bonds are formed. (1mark). Note that although there are only 3 marks for this question there are four permitted answers you only have to give three of them to get full marks.

Crude oil is a mixture of many hydrocarbons. The diagram shows the method used to separate crude oil.

Heated crude oil in

fuel gaspetrol

paraffin

diesel

fuel

bitumen

naptha

Li

Na Ar

K Sb Te

Below is part of a periodic table

a) Which of antimony (Sb) or Tellurium (Te) is most likely to be a metal?……………………………………………………………………………………….(1 mark)b) Use your knowledge of trends in the periodic table to complete the following table. (3 marks)

metal Melting point (°C) Reaction with water Colour of compounds

Li 180 moderate white

Na fast

K 64 white

c) Most of the elements in the periodic table are arranged according to their mass. However potassium, K, and argon, Ar, have atomic masses 39 and 40 respectively. Why are they apparently placed in the wrong order ?………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….(2 marks)

Li

Na Ar

K Sb Te

Below is part of a periodic table

a) Which of antimony (Sb) or Tellurium (Te) is most likely to be a metal?…………………………………Sb…………………………………………………….(1 mark)b) Use your knowledge of trends in the periodic table to complete the following table. (3 marks)

metal Melting point (°C) Reaction with water Colour of compounds

Li 180 moderate white

Na 65 to175 fast white

K 64 Very fast/ vigorous or violent

white

c) Most of the elements in the periodic table are arranged according to their mass. However potassium, K, and argon, Ar, have atomic masses 39 and 40 respectively. Why are they apparently placed in the wrong order ?Both elements are in groups of elements with similar chemical properties (1 mark) Elements in the periodic table are arranged according to increasing atomic number or proton number (1 mark)

The following hazard symbols were on a bottle of potassium nitrate.

(a) What does the hazard symbol on the left tell you about potassium nitrate?....................................................................................................................................................... (1 mark)(b) A mixture of chemicals is used to make gunpowder.The mixture includes potassium nitrate.Suggest why it is used...................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (2 marks)(c) (i) Calculate the relative formula mass (Mr) of potassium nitrate, KNO3

(Relative atomic masses: O = 16 ; N =14 ; K = 39)..........................................................................................................................................................................................................................................................................................Relative formula mass .................................................... (2 marks)(ii) Calculate the percentage of oxygen in potassium nitrate...........................................................................................................................................................................................................................................................................................Oxygen ......................................... %

(2 marks)

The following hazard symbols were on a bottle of potassium nitrate.

(a) What does the hazard symbol on the left tell you about potassium nitrate?.It is an oxidisong agent.................................................................................................................. (1 mark)(b) A mixture of chemicals is used to make gunpowder.The mixture includes potassium nitrate.Suggest why it is used..It gives oxygen (1 mark) which is needed for burning (1 mark). NOT because it its flammable................................................................................................................................................................................................................................................................................................................. (2 marks)(c) (i) Calculate the relative formula mass (Mr) of potassium nitrate, KNO3

(Relative atomic masses: O = 16 ; N =14 ; K = 39)KNO3 = K + N + Ox3 = 39 + 14+ (3x16) .....(1 mark) .........................................................................................................................................................................................................Relative formula mass ........101............................. (1 mark) ... (2 marks)(ii) Calculate the percentage of oxygen in potassium nitrate... 3 x 16  ¸ 101 x 100 …… (1 mark) …………………………………………...........You can still get full marks on this part even if your answer was wrong on the first examiners will only penalise your mistake onceOxygen ........ .47.5 ........... (1 mark) ................... %

(2 marks)

The table below shows some bond energies.

bond Bond energy in kJ/mole

C–H 413

O=O 497

C=O 740

O—H 463

Methane burns in oxygen according to the following equation:

CH4 + 2O2 CO2 + 2H2O a) Calculate the energy change which takes place when one mole of methane is completely burned in oxygen.……………………………………………………………………………………………...................................................……………………………………………………………………………………………...................................................…………………………………………………………………………………………….............................................................................................................................................................................…................................................................................................................................................................................................................(3 marks)

b) Is the reaction between methane and oxygen endothermic or exothermic. Give your reasons...................................................................................................................................................................................................................................................................................................................................................(2 marks)

C) Suggest a use of methane gas....................................................................................................................................................................(1 mark)

The table below shows some bond energies.

bond Bond energy in kJ/mole

C–H 413

O=O 497

C=O 740

O—H 463

Methane burns in oxygen according to the following equation:

CH4 + 2O2 CO2 + 2H2O a) Calculate the energy change which takes place when one mole of methane is completely burned in oxygen.………4 x (C-H) + 2 x (O=O) – 2 x (C=O) – 4 x (O-H) = ……………………………...............................................……… 4 x(413) + 2 x (497) – 2 x (740) – 4 x (463) = ……………………………...................................................………1652 +994-1480-1852 = ……………………………………………………………………............................................. -685 kJ/mol ..............................................................................................................................................Remember reactants – products and include units ............................................................................(3 marks)

b) Is the reaction between methane and oxygen endothermic or exothermic. Give your reasons.Exothermic because heat is given out, or because the energy change is negative ................................. (2 marks)

c) Suggest a use of methane gas.As a fuel ..................................................................................................................................................(1 mark)

Hydrogen bromide (HBr) can be made by the reaction of hydrogen (H2) with bromine (Br2).

(a) The diagrams represent the outer energy levels of hydrogen and bromine atoms.Draw a similar diagram to represent a molecule of hydrogen bromide (HBr).You need show only the outer energy level (shell) electrons. (1 mark)

(b) The word equation for the reaction of hydrogen with bromine is shown below.hydrogen + bromine hydrogen bromideWrite a balanced symbol equation for this reaction......................................................................................................................................................... (2 marks)(c) Hydrogen bromide gas reacts with magnesium to form the ionic compound called magnesiumbromide. Magnesium forms Mg2+ ions and bromine forms Br- ions. What is the formula for magnesium bromide?........................................................................................................................................................ (1 mark)(d) Why does magnesium bromide have a much higher melting point than hydrogen bromide?................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (2 marks)

x

H Br

Hydrogen bromide (HBr) can be made by the reaction of hydrogen (H2) with bromine (Br2).

(a) The diagrams represent the outer energy levels of hydrogen and bromine atoms.Draw a similar diagram to represent a molecule of hydrogen bromide (HBr).You need show only the outer energy level (shell) electrons. (1 mark)

(b) The word equation for the reaction of hydrogen with bromine is shown below.hydrogen + bromine hydrogen bromideWrite a balanced symbol equation for this reaction..H2 + Br2 2HBr .............................................................................................................................. (2 marks)(c) Hydrogen bromide gas reacts with magnesium to form the ionic compound called magnesiumbromide. Magnesium forms Mg2+ ions and bromine forms Br- ions. What is the formula for magnesium bromide?.....MgBr2.........If the information is not included in the question check the data sheet ......................... (1 mark)(d) Why does magnesium bromide have a much higher melting point than hydrogen bromide?Magnesium bromide is ionic (1 mark) and a lot of energy is required to break the strong electrostatic forces between the ions. Hydrogen bromide forms simple covalent molecules (1 mark) with only weak forces between the molecules, so less energy is required to separate them. ............................................................ (2 marks)

xH Br

x

H Br

Ammonia is manufactured from nitrogen and hydrogen using the Haber process.

N2(g) + 3H2(g) 2NH3(g)

a) What does the symbol mean?........................................................................................................................ .(1 mark)

b) Why is the manufacture of ammonia carried out at high pressure.................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (2 marks)c) Low temperatures favour a high yield in the Haber process. Explain whether the process is carried out at high temperatures or low temperatures.Use ideas about collisions between particles in your answer........................................................................................................................................... .......................................................................................................................................... ................................................................................................................................................................................................................................................................. (3 marks)d) Ammonia is reacted with nitric acid to make ammonium nitrate. Ammonium nitrate isUsed as nitrogen source for plants.Why do plants need nitrogen?......................................................................................................................................... ................................................................................................................................ (2 marks)

Ammonia is manufactured from nitrogen and hydrogen using the Haber process.

N2(g) + 3H2(g) 2NH3(g)

a) What does the symbol mean?.........This means the reaction is reversible........................................................ .(1 mark)

b) Why is the manufacture of ammonia carried out at high pressure.Increasing the pressure will increase the rate of collisions so will increase the rate ofreaction. Also there are fewer molecules on the right hand side of the equation than on the right, increasing the pressure will force the equilibrium to the side with the least number of molecules, this will increase the yield..........................................................Note: this is difficult because it is asking you to apply knowledge from different bits of the.course ‘rates’ and ‘equilibria’. This is oftent he case in questions about ammonia.(2 marks)c) Low temperatures favour a high yield in the Haber process. Explain whether the process is carried out at high temperatures or low temperatures.Use ideas about collisions between particles in your answer.The yield may be high at low temperatures but the rate of reaction will very slow (1 mark this is because the gas particles will have less energy and there will be fewer successful collisions(1 mark) A higher temperature is used so that ammonia can be produced more quickly (1 mark)Note: If the question asks you to use collision theory in your answer, use it! .(3 marks)d) Ammonia is reacted with nitric acid to make ammonium nitrate. Ammonium nitrate isUsed as nitrogen source for plants.Why do plants need nitrogen?.....To make protein (1 mark) for growth (1 mark) .................................................................................... ................................................................................................................................ (2 marks)

(a) The diagram shows a blast furnace used to extract iron from iron ore.

Complete the diagram by adding the three missing labels. (3 marks)(b) An important reaction in this process is represented by this equation.(i) Balance the equation.Fe2O3 + ....CO .......Fe + 3CO2

(1 mark)(ii) Which substance has been reduced in this reaction?.............................................................................................................................................. (1 mark)(iii) What is the purpose of the limestone in this reaction?.............................................................................................................................................. (1 mark) (c) Aluminium is made by the reduction of molten aluminium ore, using a very large amountof electricity.Suggest why aluminium is more expensive than iron.............................................................................................................................................................................................................................................................................(1 mark)

Blasts of hot air

Iron ore,____ and limestone

Molten slagMolten ____

(a) The diagram shows a blast furnace used to extract iron from iron ore.

Complete the diagram by adding the three missing labels. (3 marks)(b) An important reaction in this process is represented by this equation.(i) Balance the equation.Fe2O3 + 3CO .2.Fe + 3CO2

(1 mark)(ii) Which substance has been reduced in this reaction?...............iron........................................................................................................................... (1 mark)(iii) What is the purpose of the limestone in this reaction?..............to react with the impurities, ........................................................................................ (1 mark) (c) Aluminium is made by the reduction of molten aluminium ore, using a very large amountof electricity.Suggest why aluminium is more expensive than iron.the fuel costs of producing aluminium are much higher than those for the production of iron(1 mark)

Blasts of hot air

Iron ore, coke and limestone

Molten slagMolten iron

waste gases

The table below gives information about the atomic structure of some elements

element protons Electron arrangement

group Metl/non-metal

A 6 4 Non-metal

B 19 2,8,8,1 metal

C 2,8 0 Non-metal

D 17 2,8,7 7

a) Fill in the blank spaces in the table (4 marks)

b) Which element will react with element D to form an ionic compound?.......................................................................................................................................... (1 mark) c) Which element is monotomic?

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

d) Draw a diagram to show the bonding in element B (2 marks)

The table below gives information about the atomic structure of some elements

element protons Electron arrangement

group Metl/non-metal

A 6 2,4 4 Non-metal

B 19 2,8,8,1 1 metal

C 10 2,8 0 Non-metal

D 17 2,8,7 7 Non-metal

a) Fill in the blank spaces in the table (4 marks)

b) Which element will react with element D to form an ionic compound?............................................................B.......................................................................................... (1 mark) c) Which element is monotomic?

..............................................................C this means that it exists as single atoms.........................(1 mark)

d) Draw a diagram to show the bonding in element B

-++ + ++ + +

++ + ++ + +++ + ++ + +

++ + ++ + +-

-

-

-

- -

-

--- -

---

-

--

- --

-

-

-

--

--

Negative electronsPositive metal ions

Note your diagram can be simpler than this, just show positive stationary metal ions and negative mobile electrons