# Chemistry 2017 Past Questions | WAEC

Study the following Chemistry past questions and answers for JAMBWAEC  NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

## Chemistry 2017 Theory

1. (a)(i) What is an acid-base indicator?

(ii) Give one example of an acid-base indicator.

(b) State the property exhibited by nitrogen(IV) oxide in each of the following equations:,

(i) 4Cu + 2NO$$_2$$ -> 4CuO + N$$_2$$ (ii) H$$_2$$O + 2NO$$_2$$ –> HNO$$_3$$ + HNO$$_2$$

(c)(i) Define enthalpy of combustion..

(ii) State why the enthalpy of combustion is always negative.

(d)(i) Distinguish between a primary cell and a secondary cell.

(ii) Give an example of each of the cells stated in I (d)(i).

(e) Define the term mole.

(f) Calculate the amount of hydrochloric acid in 40.0 cm$$^3$$ of 0.40 moldm$$^{-3}$$ dilute HCl.

(g) Name two substances which can be used as electrodes during the electroylsis of acidified water.

(h) List two forces of attraction that can exist between covalent molecules.

(i) Name the products formed when butane undergoes incomplete combustion.

(j) Write the electron configuration of $$_{26}$$Fe$$^{3+}$$

2. (a)(i) 1. State the periodic law.

2. What is meant by the term periodic property of elements?

(ii) List three properties of an element which show periodicity.

(iii) Explain briefly how each of the properties listed in (a)(i) in varies across the period.

(b) Defulle relative atomic mass.

(c)(i) What phenomenon is exhibited by an element Z which exist as $$^{35}_{17}Z$$ and $$^{37}_{17}X$$

(ii) What accounts for the difference in the mass numbers of the element Z?

(iii) Calculate the relative atomic mass of Z if the percentage abundance of $$^{37}_{17}Z$$ is 75%

(d)(i) State the method used for collecting each of the following gases: I. CO II. HCI  III. H$$_2$$

(ii) Give a reason for your answer stated in (d)(i) I and II

3. (a) Write the molecular formula of X.

(i) What type of reaction is represented by the equation?

(ii) Consider the following reaction equation: C$$_{12}H_2$$ $$\to$$ X + C$$_8$$H$$_{18}$$

(iii) Draw the structure of two isomers of X.

(iv) Name the isomers drawn in (a)(iii).

(v) Write a balanced equation for the reaction between X and hydrogen.

(b) Describe one test for fats.

(c) Sulphur (IV) oxide is converted to tetraoxosulphate (VI) acid according to the following equation: 2SO$$_{2(g)}$$ + O$$_{2(g)}$$ + 2H$$_2$$O$$_{(l)}$$  $$\to$$  2H$$_2$$OSO$$_{4(aq)}$$. If 1.5 moles of oxgen reacts with sulphur (IV) oxide, calculate the mass of tetraoxosulphate (VI) acid produced. [H = 1.0; O = 16.0; S = 32.0].

(d) Consider the following neutralization reaction:

CH$$_3$$COOH + NaOH $$\to$$ CH$$_3$$COONa + H$$_2$$O;  $$\bigtriangleup$$H$$_1$$

CH$$_3$$COOH + NH$$_4$$OH $$\to$$ CH$$_3$$COONH$$_4$$ + H$$_2$$O;  $$\bigtriangleup$$H$$_2$$

NaOH + HCl $$\to$$ NaCl + H$$_2$$O  $$\bigtriangleup$$H$$_3$$

(i) Arrange the enthalphy changes for the reactions in order of increasing magnitude.

(ii) Explain briefly your order in (d)(i).

(e) Consider the following substances. Cu$$_{(s)}$$, BeCl$$_2$$, NaH$$_{(s)}$$, HF$$_{(s)}$$and CCl$$_{4(l)}$$. State the substance(s) which;

(i) can conduct electricity;

(ii) is/are soluble in water.

4. (a)(i) State two industrial uses of hdrogen.

(ii) Consider the equation below. Mg(HCO

1. State the type of hardness of water being removed as shown by the above equation.

2. Give two disadvantages of hardness of water.

(b)(i) In the extraction of aluminium by electrolysis, graphite electrodes are used. State the disadvantages of using this type of electrode.

(ii) Calcuim oxide reacts with water to form slaked line: I. Write a balanced equation for this reaction; II. State one use of slaked line.

(c)(i) What is meant by saponification?

(ii) List the raw materials needed for the manufacture of soap.

(iii) Name the main by-product obtained from the manufacture of soap.

(d) With the aid of chemical equations explain briefly how iron is extracted in the blast furnace using iron ore, coke and limestone as raw materials at the:

(i) bottom of the furnace; (ii) middle of the furnace (iii) top of the furnace.

5. (a)(i) Describe briefly how trioxonitrate (V) ions could be tested for in the laboratory.

(ii) State two uses of each of the following compounds: I. sodium chloride; II. sodium trioxocarbonate (IV).

(b) Write balanced equations for the reactions involved in the extraction of iron in the blast furnace.

(ii) State Faraday’s first law of electrolysis.

(iii) State two applications of electrolysis.

(c) Concentrated tetraoxosulphate (VI) acid is added to sugar crystals in a beaker. State what would be observed. Explain briefly your answer.

(d) Write an equation for the reaction of zinc powder with:

(i) dilute tetraoxosulphate (VI) acid;

(ii) concentrated tetraoxosulphate (VI) acid.

(e) What property of concentrated tetraoxosulphate (VI) acid is shown in (d)(ii)

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