ACIDS, BASES AND SALTS
QUESTIONS:
1. Multiple choice.
Choose the most correct answer from the given alternatives at each item.
(i)An alkali can be defined as
A: any insoluble salt B: any soluble salt D: any insoluble base D: any soluble base
(ii) Indicators are chemical substances which used to
A: measure pH B: measure volume of an acid C: show colour change D: form pinccolour with acid
(iii) The blue colour of the litmus paper means the litmus paper is
A: in acidic medium B: neutral C: in alkaline medium D: blue when placed in strong acid
(iv) The following is a basicity of the sulphuric acid.
A: 2 B: 3 C: 1 D: 4
(v) At neutralization point, the pH scale is
A: 14 B: 7 C: 3 D: 5
(vi) Salts which are _____ and ____ can be used as drying agents.
A: hygroscopic and deliquescent B: deliquescent and efflorescent
C: hygroscopic and efflorescent D: acidic and basic
(vii) Lizbeth has substance X, that substance found to have neither OH- nor H+ there fore the substance X is
A: a weak acid B: weak base C: strong base D: neither acidic nor basic
(viii) If the solution has sour taste, it means the substance is
A: an alkali B: basic C: acidic D: salt
(ix) When methyl orange drops added to acidic solution the mixture turns to
A: red B: Pink C: orange D: yellow
(x) When H+ of an acid replaced by metal or ammonium ion ____ is formed.
A: Indicator B: soap C: salt D: acidic salt
2. Matching items.
Match list A with items in list B.
List A.
(i) soluble salts
(ii) insoluble salt
(iii) basicity of acid
(iv) neutralization
(v) strong acids
(vi) strong bases
(vii) weak acids
(viii) weak bases
(ix) acidic solution
(x) normal salts.
List B.
A: Has pH less than 7.
B: Has pH which is above 7.
C: Number of hydrogen atoms in a molecules which can be displaced by metal.
D: K2CO3 and ZnCl2
E: NaHSO4 and Na2SO4
F: Dilute nitric acid
G: concentrated sodium hydroxide.
H: Lead sulphate and calcium sulphate
I: sodium carbonate and potassium chloride.
J: acid base reaction resulting 7 pH.
K: Ethanoic acid and carbonic acid.
L: Hydrochloric acid and sulphuric acid
M: Sodium hydroxide and potassium hydroxide.
N: Sodium hydrogen carbonate and ammonium hydroxide.
3. Differentiate alkali from base.
4. What do the following terms mean?
(a) An acid
(b) Base
(c) Salt
(d) Indicator
(e) Basicity of acids.
5. Describe three types of salts basing on the pH.
6. State results for these salts when heat energy acts on them.
(a) Hydrated copper (ii) sulphate
(b) Copper carbonate
(c) Ammonium carbonate
(d) Ammonium nitrate
(e) Potassium nitrate.
7. Explain the meaning of :-
(i) Strong acid or base
(ii) Weak acid or base
8. Explain how soluble salts and insoluble salts prepared?
9. Analyse:-
(a) three chemical properties of acids and three chemical properties of base.
(b) by using their physical properties , show difference between acid and base.
10. List down three uses of each of the following substances:-
(a)salts
(b) bases
(c)acids
11. Group the following salts into soluble salts and soluble salts.
A-copper sulphate
B-silver chloride
C-sodium chloride
D-sodium carbonate
E-calcium carbonate
F-lead sulphate
G-silver nitrate
H-barium sulphate
ANSWERS:
1. (i) D vi) A
(ii) A vii) D
(iii) C viii) C
(iv) A ix) B
(v) B x) C
2. (i) I vi) M
(ii) H vii) K
(iii) C viii) N
(iv) J ix) F
(v) L x) D
3. An alkali is any base which is soluble While base is a substance which contains hydroxide ions (OH-)
4. (a) An acid is a compound that when dissolved in water produces hydrogen ions and pH less than 7.
(b) Base is a compound that when dissolved in water produces hydroxide ions and pH above 7.
(c) Salt is a substance which formed when the hydrogen ion of an acid is replaced directly or indirectly by metal or ammonium ion.
(d) Indicator is a compound that shows a definite colour change in an acid or base.
For example. Methyl orange and phenolphthalein indicator.
(e) Basicity of acids refers to number of hydrogen atoms per molecules that can be displaced by the metal.
5. We have three types of salts basing on pH factor which are:-
i) Acidic salts
ii) Basic salts
iii) Normal salts
• Acidic salts are salts which formed when only part o replaceable hydrogen ions per molecule is replaced.
Examples of acidic salts.
-NaHPO4
-NaHCO3
• Basic salts are salts formed when amount of acid required to neutralise base is insufficient.
Examples of basic salts.
-basic zinc chloride (ZnCl2•Zn(OH)2)
-basic magnesium chloride (MgCl2•Mg(OH).
• Normal salts are salts that formed when all replaceable hydrogen ions of acids are replaced by metals.
Examples of normal salts
-Ammonium sulphate
-Potassium carbonate.
-Zinc chloride
6. (a) water lost and its blue colour disappear then the salt becomes white or black when it is heated strongly.
(b) Copper oxide and carbon dioxide are formed.
(c) ammonia gas, water and carbon dioxide are formed.
(d) dinitrogen oxide and water are formed.
(e) brown fumes if potassium nitrogen dioxide and oxygen are produced.
7. (b) Strong acids or bases are acids or bases that dissociate completely in water. Acids produce hydrogen ions while bases produces hydroxide ions after being dissociated in water.
(b) weak acids or bases are acids or bases which dissociate partially in water.
Acids produce few hydrogen ions while bases produce few hydroxide ions.
8. •Soluble salts prepared by reacting acids with either metals, alkalis or insoluble bases or carbonate.
Whereby hydrogen atoms from acids displaced by metals.
For example.
-Zn + H2SO4 ------> ZnSO4 + H2
-H2SO4 + 2NaOH -----> Na2SO4 + 2H2O
•Insoluble salts prepared by precipitation or double decomposition method , whereby two soluble salts react to produce two salts in which one is insoluble.
For example.
Pb(NO3)2 (aq) + 2KI(aq) ------> PbI2(s) + 2KNO3(aq)
Lead iodide is insoluble salt.
9. (a) •Chemical properties of acids.
-dilute acids react with some metals to salt and hydrogen gas.
For example.
Zn(s) + HCl(aq) -----> ZnCl2(aq) + H2(g)
-they react with bases to form salt and water.
For example.
HCl(aq) + NaOH(aq) -------> NaCl(aq) + H2O(l).
-They react with carbonates or hydrogen carbonates to produce salts, water and carbon dioxide.
For example.
2HCl(aq) + CaCO3(s) ------> CaCl2(aq) + 2H2O(l) + CO2(g).
-They have pH less than 7.
•Chemical properties of bases.
-They react with acids to produce salts and water.
-Soluble bases precipitate insoluble metal hydroxides from their salt solution.
For example.
3KOH(aq) + FeCl3(aq) ------> Fe(OH)3(s) + 3KCl(aq).
-They react with amnonium salts to produce ammonia gas.
For example.
2NH4Cl(s) + Ca(OH)2(aq) -----> CaCl2(aq) + 2H2O(l) + 2NH3(g).
-They have pH above 7.
(b) •Acids have sour taste While bases have bitter taste.
•Acids turn blue litmus paper red While bases turn red litmus paper red.
10. • The following are uses of salts.
-to control soil pH.
-used as fertilizers
-to soften hard water(eg. Na2CO3)
-used as electrolyte(eg. NH4Cl)
-to alleviate health disorders
•Uses of bases.
-Used in preparation of salts
-used as reagents in the laboratory
-used in preparation of soaps.
•Uses of acids.
-used in preparation of salts
-used as reagents in the laboratory
- used in digestion process.
11. •soluble salts are. A, C, D and G.
•insoluble salts are B, E, F and H.
No comments