chemistry mid tes

1.    Substance X was electrolysed in an electrolytic cell. A coloured gas was formed at the anode and a metal was formed at the cathode.

What is substance X?

A.      aqueous sodium chloride                                             C. molten zinc oxide

B.      molten lead bromide                                                     D. solid sodium chloride

2.    The diagram shows the electrolysis of concentrated aqueous sodium chloride.

What is the colour of the Universal Indicator at each electrode after five minutes?

	Colour at anode (+ electrode)	Colour at cathode ( - electrode)
A	Blue / purple	Red
B	Red	Blue/purple
C	Red	Colourless
D	Colourless	Blue / purple

3.    Which diagram shows an experiment in which the bulb lights?

4.    Copper and hydrogen can each be formed by electrolysis.At which electrodes are these elements formed?

	Copper	Hydrogen
A	Anode	Anode
B	Anode	Cathode
C	Cathode	Anode
D	Cathode	Cathode

5.    The electrolysis of concentrated aqueous sodium chloride makes three products.Which products are shown at the correct electrodes?

	Anode (+ve)	Cathode (-ve)
A	Chlorine	Sodium hydroxide
B	Sodium hydroxide	Chlorine
C	Hydrogen	Sodium
D	Sodium	Hydrogen

6.    Which equation shows an oxidation reaction?

A.      C + O₂→ CO₂                                                      C. 2H₂O₂→ 2H₂O + O₂

B.      CaCO₃→ CaO + CO₂                                         D. N₂O₄ → 2NO₂

7.    Carbon dioxide is an acidic oxide that reacts with aqueous calcium hydroxide.Which type of reaction takes place?

A.      Decomposition                 B. fermentation                                C. neutralisation                               D. oxidation

8.    Which is not a typical property of an acid?

A.   They react with alkalis producing water.

B.   They react with all metals producing hydrogen.

C.   They react with carbonates producing carbon dioxide.

D.   They turn litmus paper red.

9.    A solution contains barium ions and silver ions.

What could the anion be?

A.      chloride only                                                      C. nitrate only                   

B.      sulfate only                                                        D. chloride or nitrate or sulfate

10.Which process is endothermic?

A.      adding water to anhydrous copper(II) sulphate

B.      burning magnesium to make the oxide

C.      heating water to make steam

D.      neutralising acidic industrial waste

11.      When ammonium nitrate is added to water, an endothermic reaction occurs and?

A.     the surroundings get hotter                      C. heat is given out

B.     the temperature rises                                 D. the temperature falls

12.   Which diagrams show a process in which an exothermic change is taking place?

A.  1 and 2 only                                                        C. 1 and 3 only                  

B.  2 and 3 only                                                        D 1, 2 and 3

13.   In different experiments, 2 g of marble are added to 10 cm3 of hydrochloric acid.In which tube is the reaction fastest?

14.      For the reaction: 3H₂ + N₂à 2NH₃
The breaking of bonds in a hydrogen molecule when it combines with nitrogen to formammonia must be?

A.     Endothermic                                                    C.   electrolytic

B.     Electrostatic                                                     D.  exothermic

15.      The reaction between hydrogen and chlorine to form hydrogen chloride can be written as:
H₂(g) + Cl₂(g) à2HCl(g)
Use the bond energies shown to calculate the energy change that takes place when hydrogen chloride is formed according to the above equation. (Bond energies in kJ/mol: H-H 435, Cl-Cl 245, H-Cl 430)

A.     90 kJ given out                                                                C. 250 kJ taken in

B.     180 kJ given out                                              D. 125 kJ taken in

16.      When an exothermic reaction takes place, the reaction mixture gets hotter because?

A.     energy is always released in a chemical change which makes new substances

B.     more energy is absorbed when new bonds are made than is needed to break existing bonds

C.     in an exothermic change the products are more stable than the reactants

D.     exothermic changes always produce gases

17.      Calcium carbonate in the form of limestone dissolves in hydrochloric acid and giving off carbon dioxide gas. Which conditions would produce the fastest reaction?

A.     temperature of 40°C and 10cm³ of dilute acid

B.     temperature of 40°C and 5cm³ of dilute acid and 5cm³ of water

C.     temperature of 20°C and 10cm³ of dilute acid

D.     temperature of 20°C and 5cm³ of dilute acid and 5cm³ of water

18.      Which mixture will produce the slowest reaction to take place between solid calcium carbonate (marble chips) and dilute hydrochloric acid?

A.     large chips, concentrated acid, low temperature

B.     low temperature, largel chips, dilute acid

C.     concentrated acid, high temperature, small chips

D.     high temperature, small chips, dilute acid

19.      Acids react with bases, carbonates and metals.Which of these reactions produce a gas?

	Reaction of acid with
	Base	Carbonate	Metal
A	√	√	√
B	√	X	X
C	X	√	√
D	X	√	X

20.   The diagram shows the position of an element X in the Periodic Table.

What is the correct classification of element X and its oxide?

	X	Oxide of X
A	Metal	Acidic
B	Metal	Basic
C	Non-metal	Acidic
D	Non-metal	Basic

B.Give a clear and complete answer for each number below! The total score for this part is 50

21.      The diagram shows the apparatus used by a student to find the concentration of  hydrochloric acid. Sodium hydroxide solution was added to hydrochloric acid until the solution was neutral.

(a) Complete the boxes to name the apparatus used. [3]

(b) How could the student tell when the solution was neutral?

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

..................................................................................................................................... [2]

[Total: 5]

22.      The apparatus below was used to deposit a thin layer of chromium on a steel knife.

The knife was cleaned carefully and all grease removed before the process started.

(a) What is the name of the process when metal objects are coated with other metals?

..................................................................................................................................... [1]

(b) (i) Suggest the identity of metal A.

......................................................................................................................................[1]

(ii) Suggest the name of salt B.

.............................................................................................................................. …….[1]

(c) Give two reasons why steel knives are coated with chromium.

1. ..................................................................................................................................

2. ................................................................................................................................. [2]

[Total: 5]

23.   The electrolysis of concentrated aqueous sodium chloride, between inert electrodes, is used

to make three important chemicals.  (Total : 8)

hydrogen

chlorine

sodium hydroxide

 (a) The ions present in the electrolyte are Na⁺, H⁺, C ^– and OH^–.

(i) Hydrogen ions are discharged at the negative electrode (cathode).

Write an equation for this reaction.

.............................................................................................................................. [2]

(ii) The hydrogen ions are from the water.

H₂O à H⁺ + OH ^–

Suggest an explanation why the concentration of hydroxide ions increases.

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

.............................................................................................................................. [2]

(iii) When a dilute solution of sodium chloride is used, chlorine is not formed at the

positive electrode (anode), a different gas is produced. Name this gas.

.............................................................................................................................. [1]

(iv) State an example of an inert electrode.

.............................................................................................................................. [1]

(b) (i) State a use of hydrogen.

.............................................................................................................................. [1]

(ii) Why is chlorine used to treat the water supply?

.............................................................................................................................. [1]

24.Soluble salts can be made using a base and an acid.

(a) Complete this method of preparing dry crystals of the soluble salt cobalt(II) chloride-6-water from the insoluble base cobalt(II) carbonate.

Step 1       

Add an excess of cobalt(II) carbonate to hot dilute hydrochloric acid.

Step 2

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Step 3

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Step 4

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............................................................................................................................. [Total 4]

25. A student used the apparatus shown below to investigate the speed of reaction when large

lumps of zinc reacted with excess sulfuric acid.

zinc + sulfuric acid → zinc sulfate + hydrogen

(a) As the reaction proceeds, describe what happens to

(i) the mass of the zinc lumps.

.............................................................................................................................. [1]

(ii) the concentration of zinc sulfate in the solution in the fl ask.

.............................................................................................................................. [1]

(b) The student’s results are shown below.

(ii) Use your graph to calculate the volume of hydrogen given off after 25 minutes.

volume of hydrogen ............................................................................................. [1]

(iii) Explain why no more hydrogen was given off after 50 minutes.

.......................................................................................................................................[1]

(iv) Describe a test for hydrogen.

test .............................................................................................................................

result .................................................................................................................... [2]

(c) What happens to the speed of the reaction when

(i) smaller pieces of zinc are used?

.............................................................................................................................. [1]

(ii) some water is added to the sulfuric acid?

.............................................................................................................................. [1]

(d) The reaction between zinc and sulfuric acid is catalysed by copper(II) sulfate solution.

What do you understand by the term catalyst ?

..................................................................................................................................... [1]

[Total: 12]

26.  A student investigated the addition of four different solids, A, B, C and D, to water.

Five experiments were carried out.

Experiment 1

By using a measuring cylinder, 30 cm3 of distilled water was poured into a polystyrene cup

and the initial temperature of the water was measured. 4 g of solid A was added to the cup

and the mixture stirred with a thermometer. The temperature of the solution was measured after 2 minutes.

Experiment 2

Experiment 1 was repeated using 4 g of solid B.

Experiment 3

Experiment 1 was repeated using 4 g of solid C.

Experiment 4

Experiment 1 was repeated using 4 g of solid D.

Experiment 5

A little of the solution from Experiment 4 was added to a little of the solution from

Experiment 2 in a test-tube. The observations were recorded.

Observations A fast reaction. Vigorous effervescence and bubbles produced.

(a) Use the thermometer diagrams for Experiments 1-4 to record the initial and final temperatures in Table 4.1. Calculate and record the temperature difference in Table 4.1.

(b) Draw a labelled bar chart of the results to Experiments 1, 2, 3 and 4 on the grid below.

Use the results and observations from Experiments 1-5 to answer the following questions.

(c) (i) Which solid dissolves in water to produce an exothermic reaction? [1]

           ……………………………………………..

(ii) Give a reason why you chose this solid. [1]

            …………………………………………………

(d) Which Experiment produced the largest temperature change? [1]

       …………………………………………………….

(e) Predict the temperature change that would happen if

(i) 8 g of solid B were used in Experiment 2, [1]

     ……………………………………………………………………………………………………………………………………

(ii) 60 cm³ of water was used in Experiment 4. [1]

     ………………………………………………………………………………………………………………………………………

(iii) Explain your answer to (e)(ii). [1]

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

(f) Suggest an explanation for the observations in Experiment 5. [2]    

      ……………………………………………………………………………………