Waec Chemistry Questions
Question 1597:
(a) Explain briefly why \(_2^4He\) has a stable electron configuration compared to \(_4^9Be\)
(b) Consider the following elements: 1H and 3Li.
(i) State the number of electrons that an atom of each element would have after forming an ionic bond.
(ii) Give a reason for each of your answers stated in (b)(i).
(c) State two factors that should be considered when siting a chemical industry.
(d) State two advantages of using a catalyst instead of high temperatures in chemical reactions.
(e) Turpentine burns in chlorine according to the following equation:
C\(_{10}\)H\(_{16}\)\(_{(I)}\) + 8Cl\(_{2(g)}\) \(\to\) 10C\(_{(s)}\) + 16HCl\(_{(g)}\)
Calculate the mass of turpentine that would completely burn in 21.3 g of chlorine.
[Molar mass of chlorine = 71 gmol\(^{-1}\); Molar mass of Turpentine = 136 gmol\(^{-1}\)]
(f) What is cracking?
(g) State two factors that may influence the value of electron affinity.
(h) What are carbohydrates?
(i) State two differences between a simple sugar and starch.
(j) Write an equation to show the dissociation of each of the following acids:
(i) H\(_2\)CO\(_3\);
(ii) CH\(_3\)COOH.
View Answer & Explanation(b) Consider the following elements: 1H and 3Li.
(i) State the number of electrons that an atom of each element would have after forming an ionic bond.
(ii) Give a reason for each of your answers stated in (b)(i).
(c) State two factors that should be considered when siting a chemical industry.
(d) State two advantages of using a catalyst instead of high temperatures in chemical reactions.
(e) Turpentine burns in chlorine according to the following equation:
C\(_{10}\)H\(_{16}\)\(_{(I)}\) + 8Cl\(_{2(g)}\) \(\to\) 10C\(_{(s)}\) + 16HCl\(_{(g)}\)
Calculate the mass of turpentine that would completely burn in 21.3 g of chlorine.
[Molar mass of chlorine = 71 gmol\(^{-1}\); Molar mass of Turpentine = 136 gmol\(^{-1}\)]
(f) What is cracking?
(g) State two factors that may influence the value of electron affinity.
(h) What are carbohydrates?
(i) State two differences between a simple sugar and starch.
(j) Write an equation to show the dissociation of each of the following acids:
(i) H\(_2\)CO\(_3\);
(ii) CH\(_3\)COOH.
Question 1598:
(a) (i) Name three different methods for preparing salts.
(ii) Give one example of a balanced equation for each of the methods named in (a)(i).
(iii) State two uses of sodium trioxocarbonate (IV).
(b) If you were given some impure copper, describe how you would
obtain a specimen of the pure metal by electrolysis.
(c) Given that sodium chloride has a solubility of 36.3 at 30 and 39.0 at
100 and that of silver nitrate is 297.0 at 30 and 952.0 at 100.
(i) Calculate the percentage of each substance in the saturated solution at 100 that is deposited on cooling to 30
(ii) Deduce which of the two salts can be purified more efficiently by crystallization.
View Answer & Explanation(ii) Give one example of a balanced equation for each of the methods named in (a)(i).
(iii) State two uses of sodium trioxocarbonate (IV).
(b) If you were given some impure copper, describe how you would
obtain a specimen of the pure metal by electrolysis.
(c) Given that sodium chloride has a solubility of 36.3 at 30 and 39.0 at
100 and that of silver nitrate is 297.0 at 30 and 952.0 at 100.
(i) Calculate the percentage of each substance in the saturated solution at 100 that is deposited on cooling to 30
(ii) Deduce which of the two salts can be purified more efficiently by crystallization.
Question 1599:
(a) (i) State the important points put forward in Dalton’s atomic theory.
(ii) How does the theory explain the law of multiple proportion?
(b) (i) Name three commercially useful products that may be obtained by chemical transformation of vegetable oils.
(ii) With the aid of equations, describe the chemical reaction involved in the transformations stated in (b)(i).
(c) Certain properties of Beryllium (Be) and its compounds differ from those of Magnesium (Mg) and its compounds, but rather resembles those of Aluminium and its compounds. Explain briefly why this is so.
(d) Write balanced equation for the reaction between iodine and aqueous sodium trioxothiosulphate(VI).
View Answer & Explanation(ii) How does the theory explain the law of multiple proportion?
(b) (i) Name three commercially useful products that may be obtained by chemical transformation of vegetable oils.
(ii) With the aid of equations, describe the chemical reaction involved in the transformations stated in (b)(i).
(c) Certain properties of Beryllium (Be) and its compounds differ from those of Magnesium (Mg) and its compounds, but rather resembles those of Aluminium and its compounds. Explain briefly why this is so.
(d) Write balanced equation for the reaction between iodine and aqueous sodium trioxothiosulphate(VI).
Question 1600:
(a) (i) What is meant by hardness of water?
(ii) Describe briefly how you would determine what proportion of hardness in a given sample of water is due to permanent hardness.
(iii) Give two reasons why hardness of water is an undesirable property.
(b) State the:
(i) reagents;
(ii) conditions for the laboratory preparation of trioxonitrate (V) acid.
(iii) How does concentrated trioxonitrate (V) acid reacts with:
(I) sulphur;
(II) aluminium.
(c) Name one amphoteric oxide.
View Answer & Explanation(ii) Describe briefly how you would determine what proportion of hardness in a given sample of water is due to permanent hardness.
(iii) Give two reasons why hardness of water is an undesirable property.
(b) State the:
(i) reagents;
(ii) conditions for the laboratory preparation of trioxonitrate (V) acid.
(iii) How does concentrated trioxonitrate (V) acid reacts with:
(I) sulphur;
(II) aluminium.
(c) Name one amphoteric oxide.