ICSE-X-Chemistry
03: Acids, Bases and Salts
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- #6-a-iinitric acidAns : Nitric acid: N2O5
- #6-a-iiiphosphoric acidAns : Phosphoric acid: P2O5
- #6-a-ivcarbonic acidAns : Carbonic acid : CO2
- #6-bacids present in vinegar, grapes and lemonAns : Acids present in following are:
Vinegar: Acetic acid
Grapes: Tartaric acid and Malic acid
Lemon: Citric acid
- #6-c-iion that turns blue litmus red,Ans : H+ ion turns blue litmus red.
- #6-c-iiion that turns red litmus blue.Ans : OH- ion turns red litmus blue.
- Qstn #7What do you understand by the statement ‘acetic acid is a monobasic acid?Ans : 7 Acetic acid is a monobasic acid which on ionization in water produce one hydronium ion per molecule of the acid.
- #8Ans : 8
- #8-aGive a balanced equation for reaction of nitrogen dioxide with water.Ans : 2NO2 + H2O → HNO2 + HNO3
- #8-bHow many types of salts does dibasic acid produce when it reacts with caustic soda solution? Give equation(s)Ans : Two types of salts are produced when dibasic acid reacts with caustic soda. One is acidic salt and other normal salt.
Acid salts:
H2SO4 + NaOH → NaHSO4 + H2O
Normal salts:
H2SO4 + 2NaOH → Na2SO4 + 2H2O
- Qstn #9Carbonic acid gives an acid salt but hydrochloric acid does not. Explain.Ans : 9 The strength of an acid is the extent to which the acid ionizes or dissociates in water. The strength of an acid depends on the degree of ionization and concentration of hydronium ions [H3O+] produced by that acid in aqueous solution.
- Qstn #10What do you understand by the strength of an acid? On which factor does the strength of an acid depend?Ans : 10
(a) Carbonic acid is a dibasic acid with two replaceable hydrogen ions; therefore it forms one acid salt or one normal salt.
Hydrochloric acid is a monobasic acid with one replaceable hydrogen ion and so forms only one normal salt.
(b) Strength of an acid is the measure of the concentration of hydronium ions it produces in its aqueous solution. Dil. HCl produces high concentration of hydronium ion compared to that of concentrated acetic acid. Thus, dil. HCl is stronger acid than highly concentrated acetic acid.
(c) H3PO3 is not a tribasic acid because in oxyacids of phosphorus, hydrogen atoms which are attached to oxygen atoms are replaceable. Hydrogen atoms directly bonded to phosphorus atoms are not replaceable.
(d) The salt produced is insoluble in the solution so the reaction does not proceed. Hence, we do not expect lead carbonate to react with hydrochloric acid.
(e) NO2 is called double acid anhydride because two acids - nitrous acid and nitric acid - are formed when it reacts with water.
2NO2 + H2O → HNO2 + HNO2
- Qstn #11Dil. HCI acid is stronger than highly concentrated acetic acid. Explain.Ans : 11 Acid am is a by products of a variety of human activities which release oxides of sulphur and nitrogen in the atmosphere. Burning of fossil fuels, coal, oil, petrol and diesel produces sulphur dioxide and nitrogen oxide which pollute the air. Polluted air also contains many oxidising agents which produce oxygen because of excessive heat. This oxygen combines with the oxides of sulphur and nitrogen and rain water to form acids.
2SO2 + O2 + 2H2O → 2H2SO4
4NO2 + O2 + 2H2O → 4HNO3
- Qstn #12How is an acid prepared from a (a) Non-metal (b) Salt?
Give an equation for each.Ans : 12 Acids are prepared from non-metals by their oxidation. For example : Sulphur or phosphorus is oxidized by conc. Nitric acid to form sulphuric acid or phosphoric acid.
S + 6HNO3 → H2SO4 + 2H2O + 6NO2
P + 5HNO3 → H3PO4 + H2O + 5NO2
Acids are prepared from salt by a displacement reaction. For example :
Nitric acid is prepared by using H2SO4 and sodium chloride.
NaCl + H2SO4 → NaHSO4 + HNO3