Acids, Bases & Salts

Ans. Zn (s) + 2NaOH (aq) — > Na₂ZnO₂ (aq) + H₂ (g)

Ans. a) The solution with pH = 0 has highest concentration of H⁺ ions

b) The solution with pH = 5 has lowest concentration of H⁺ ions.

Ans. p stands for ‘potenz’ in German meaning power, H stands for hydrogen.

Ans. Water soluble bases are called alkalies e.g., NaOH

Ans. 7.1 to 14 is the pH range for bases.

Ans. CaOCl₂ is the chloride of lime whereas CaCl₂ is calcium chloride.

Ans. The water molecules associated with crystalline solid are called water of crystallization.

Ans. Na₂CO₃.10H₂O, sodium carbonate deca-hydrate is washing soda.

Ans. Increase in H⁺ concentration will lead to decrease in pH.

Ans. Carbon dioxide, it turns lime water milky. In this way CO₂ gas is recognised.

Ans. Those indicators whose smell changes in acidic and basic solutions.

Ans. It is because 1M HCl is a strong acid and it is completely ionized in aqueous solution whereas CH₃COOH is a weak acid, so it is only partially ionized.

Ans. CaOCl₂ + CO₂ —- > C aCO₃ + Cl₂

Ans. Bring a burning matchstick near the gas. If it is burnt with a ‘pop’ sound, the gas is H₂

Ans. pH of the solution increases when it is diluted.

Ans. When pH < 5.5, the rain water becomes acidic.

Ans. Dihydrogen gas H₂

Ans. Dry HCl (g) does not form ions, therefore it does not affect dry blue litmus.

Ans. HCl is completely ionized in aqueous solution whereas acetic acid is only partially ionized in aqueous solution.

Ans. NaHCO₃ (Sodium hydrogen carbonate) and H₂SO₄ (Sulphuric acid). The gas evolved is carbon dioxide.

Ans. The acid with pH = 2 is a stronger acid.

Ans. CaSO₄. ½ H₂O (Plaster of Paris), Calcium sulphate hemihydrate.

Ans. pH of solution is measure of Hydrogen (H⁺) ion concentration, which is, in turn, a measure of acidity. It determines the strength of acid and base. Rainwater with pH = 5 is more acidic.

Ans. Water is not a good conductor of electricity. Few drops of sulphuric acid makes it better conductor of electricity.

Ans. NaCl, Na₂CO₃ are two salts belonging to sodium family.

Ans. Sea water is a better conductor due to the presence of ions.

Ans. (i) Formic acid, HCOOH

(ii) Lactic acid, CH₃-CH(OH)-COOH

Ans. NaHCO₃ is a salt that does not contain water of crystallization.

Ans. Plaster of Paris, CaSO₄. ½ H₂O

Ans. It will be sour in taste.

Ans. Those bases which are soluble in water are called alkalies. E.g., NaOH, KOH

Ans. CaOCl₂, Bleaching powder, Calcium oxy-chloride.

Ans. Na₂CO₃ (s) + 2HCl (dil) —– > 2NaCl (aq) + CO₂ (g) + H₂O (l)

Ans. Acid: HNO₃

Base: NH₄OH (i.e., Nitric acid, Ammonium hydroxide)

Ans. Add ammonium nitrate (acidic salt) to neutralize alkaline nature of soil.

Ans. Metal oxides dissolve in water to form base, basic in nature. On the other hand non-metals dissolve in water to form acids, acidic in nature.

Ans. The solid Ca(OH)₂ is slaked lime whereas clear solution of Ca(OH)₂ in water is lime water.

Ans. NaOH (aq) + HCl (aq) —- > NaCl (aq) + H₂O (l)

Ans. Baking soda is basic in nature; it will not allow milk to turn sour due to the formation of lactic acid.

Ans. Curd contains lactic acid which can make poisonous compounds with brass and copper vessels.

Ans. pH value will decrease when milk changes to curd.

Ans. The red litmus will turn blue in Na₂CO₃ solution.

Ans. Red litmus will turn blue green colour in a solution of ammonium hydroxide.

Ans. Copper chloride imparts blue green colour to the solution.

Ans. Acidic water makes aquatic species uncomfortable. Aquatic species are more comfortable in the pH 7 to 7.8.

Ans. When solution of a base is diluted, its pH decreases.

NaOH solution, Blood, Lemon juice.

Ans. Lemon Juice < Blood < NaOH solution.

Ans. At pH lower than 5.5, tooth decay becomes faster because calcium phosphate (enamel) reacts with acid and gets corroded.

Ans. CaSO4. ½ H₂O is the formula of the compound. The name of compound is ‘Plaster of Paris’ (Calcium sulphate hemihydrate)

CaSO₄.1/2 H₂O + 3/2 H₂O —– > CaSO₄. 2H₂O

Plaster or Paris                                  (Gypsum)

Ans. a) ‘A’ with pH = 3 will turn blue litmus red because it is acidic in nature.

b) ‘B’ with pH = 10.5 will turn phenolphthalein colourless to pink because ‘B’ is basic in nature.

Ans. Soil ‘B’ is acidic, therefore it needs to be treated with powdered chalk to adjust its pH because chalk is basic, which will make soil neutral.

NH₃ + H₂O + CO₂ + NaCl —- > NaHCO₃ + NH₄Cl

Ans. When brine solution is electrolyzed we get alkali (NaOH) and chlorine (Cl₂) gas, this process is called chlor-alkali process.

2NaCl (aq) + 2H₂O (l) —> 2NaOH (aq) + H₂ (g) + Cl₂ (g)

Ans. The molecules of water associated with crytstalline substance are called water of crystallization.

When hydrated copper sulphate is heated its colour changes from blue to dirty white and water droplets are formed.

CuSO₄.5H₂O ———- > CuSO₄ + 5H₂O

If we add little water to anhydrous CuSO4, we get blue colour again. It is the presence of molecules of water of crystallization which was lost on heating

CuSO₄ + 5H₂O —– > CuSO₄.5H₂O

(Anhydrous)

Ans. KCl and NaNO₃ has pH = 7

Na₂CO₃ has pH > 7

NH₄Cl has pH < 7

Ans. ‘A’ has more H+ ion concentration.

‘A’ is acidic while ‘B’ is basic.

Ans. Sodium chloride is made up of a strong base, NaOH and a strong acid HCl. Therefore, its aqueous solution is neutral in nature.

Sodium metal reacts with water to form NaOH (base) and H₂ gas

2Na (s) + 2H₂O (l) —– > 2NaOH (aq) + H₂ (g)

Ans. a) There is no effect of dry litmus on dry ammonia gas

b) Solution of ammonia will turn red litmus blue.

Ans. a) Green precipitate of Fe(OH)₂ will be formed

FeSO₄ (aq) + 2NaOH (aq) —– > Fe(OH)₂ + Na₂SO₄ (aq)

                                                      (Green ppt)

b) White precipitate of Al(OH)3 will be formed.

AlCl₃ + 3NaOH —– > Al(OH)₃ (s) + 3NaCl (aq)

                                   (White ppt)

Ans. a) Acid should be added to the water slowly with constant cooling because the reaction is highly exothermic

b) This process is called dilution.

Ans. a) Tomato contains oxalic acid

b) Vinegar contains acetic acid

c) Tamarind contains tartaric acid.

Ans. Antacids are weakly basic in nature. They neutralize excess of HCl present in our stomach and gives us relief from hyper-acidity.

Ans. The fizzing will occur more vigorously in test tube ‘A’ because HCL is a strong acid and reacts faster than acetic acid which is a weak acid.

Ans. pH of solution signifies the nature of the solution i.e., it is weakly acidic, strongly acidic, neutral weakly basic, strongly basic.

‘B with pH = 2 is strongly acidic

‘C’ with pH = 10 will turn red litmus blue.

Ans. Acid is a substance which gives H⁺ ions in an aqueous solution.

Base is substance which gives OH^– ions in the aqueous solution.

CH₃COOH is a weak acid, H₂SO₄is a strong acid.

Ans. Universal indicator is a mixture of a number of indicators. It is used to determine pH of a solution.

Ans. a) Citrix acid – Lemon, Orange

b) Oxalic acid – Tomato, Guava

c) Lactic acid – Curd, Sour milk

d) Tartaric acid – Tamarind

Ans. It is because ‘Al’ reacts with NaOH to form sodium meta-aluminate and hydrogen gas.

2Al + 2NaOH + 2H₂O —- > NaAlO₂ + 3H₂

Ans. pH = 11 is basic

pH = 5 is acidic

pH = 7 is neutral

pH = 2 is strongly acidic

Ans. Use of baking soda:

a) It is used in making of bread, biscuits, cakes

b) It is used as an antacid.

Use of Washing soda:

a) It is used as a cleansing agent

b) It is used to remove hardness of water.

Ans. ‘X’ is NaHCO3, sodium hydrogen carbonate. It is used in cooking and for curing acidity in stomach.

2NaHCO₃ —– > Na₂CO₃ + CO₂ + H₂O

Ans. a) CuSO4.5H2O (Hydrated copper sulphate)

b) CuSO4.5H2O —– > CuSO4 + 5H2O

      (Blue)             (Dirty white)

The colour changes due to the loss of molecules of water of crystallization. Colour is regained by absorbing water molecules from atmosphere containing water vapours.

Ans. a) Highly soluble bases are called alkalies e.g., KOH

b) Bee sting contains HCOOH, formic acid which causes irritation. Baking soda (basic) neutralizes HCOOH, therefore it gives relief from pain on rubbing it on sting area.

Ans. Acid will be formed in the mouth which causes tooth decay.

a) Wash your mouth with water after every meal.

b) Brush your teeth after meal. Toothpastes are basic in nature and it will neutralize the acid formed in mouth.

Ans. The reaction in which acid reacts with a base to form salt and water is called neutralization reaction e.g.,

KOH (aq) + HNO₃ (aq) —- > KNO₃ (aq) + H₂O (l)

Ans. CaSO₄. 1/2H₂O (Calcium sulphate hemihydrate)

CaSO₄.1/2 H₂O + 3/2H₂O —– > CaSO₄. 2H₂O

Ans. When sodium hydrogen carbonate (Baking soda) is heated, sodium carbonate is formed which on crystallization forms washing soda.

2NaHCO₃ ——- > Na₂CO₃ + CO₂ + H₂O

(Baking soda)

Na₂CO₃ + 10H₂O ——- > Na₂CO₃.10H₂O

(Washing soda)

Ans. FeSO₄.7H₂O is pale green in colour. It becomes dirty white on heating.

FeSO₄.7H₂O ——- > FeSO₄ + 7H₂O

If it is heated strongly Fe₂O₃ and SO₂, SO₃ gases will be formed.

2FeSO₄ ——- > Fe₂O₃ + SO₂ + SO₃

Ans. Acidic: Ammonium chloride

Basic: Sodium carbonate

Neutral: Potassium sulphate, sodium chloride.

Ans. a) Lime water will turn milky.

b) Ca(OH)₂ (aq) + CO₂ (g) —– > CaCO₃ (s) + H₂O (l)

Ans. The powder is baking powder. It consists of sodium hydrogen carbonate and tartaric acid.

NaHCO₃ gives CO₂ on heating which makes the bread cake soft and fluffy. Tartaric acid neutralizes Na₂CO₃ which is bitter in taste.

Ans. HCl and HNO₃ form H⁺ or H₃O⁺ ions in aqueous solution whereas alcohol and glucose do not dissociate into ions.

HCl + H₂O —— > H₃O⁺ + Cl^–

HNO₃ + H₂O —– > H₃O⁺ + NO₃^–

Ans. Bleaching powder is chemically CaOCl₂, calcium oxychloride

Ca(OH)₂ + Cl₂ —- > CaOCl₂ + H₂O

It is used as a disinfectant i.e., it makes water fit for drinking.

Ans. Olfactory indicators: they give different smell in acids and bases.

Dry HCl (g) does not form ions, so there is no effect on litmus.

Ans. It has one molecule of water associated with 2 molecules of CaSO₄. Water molecules are present as water of crystallization.

b) It is a mild base and it can neutralize hyper acidity without harming our body.

Ans. Bleaching powder, CaOCl₂ is formed:

CaOCl₂ + Cl₂ ——- > CaOCl₂ + H₂O

a) It is used as an oxidizing agent.

b) It is used as a disinfectant.

Ans. the molecules of water associated with crystalline substance are called ‘water of crystallisation’.

CuSO₄.5H₂O ——- > CuSO₄ + 5H₂O

When hydrated copper sulphate is heated its colour changes from blue to dirty white and water droplets are formed. If we add little quantity of water to anhydrous CuSO₄, we get blue colour again. It is those presence of molecules water of crystallisation which was lost on heating.

Activity: To study the effect of heat on hydrated crystalline salts.

i) Take 2 g of CuSO₄.5H₂O in a test tube.

ii) Observe the initial colour of the salt.

iii) Heat the test tube at top of burner carefully as shown in the diagram.

iv) Record your observations.

v) Cool the crystals and add few drops of water.

vi) Record your observations again.

Observations: Blue colour of CuSO₄.5H₂O is changed to dirty white anhydrous CuSO₄ and water droplets were formed. On adding water, blue colour of salt was restored.

Conclusion: CuSO₄.5H₂O is a hydrated salt which loses water of crystallisation, which on heating becomes dirty white and regains its colour when it comes in contact with water.

Chemical reactions involved:

CuSO₄.5H₂O (s) —— > CuSO₄ (s) + 5H₂O (l)

(Blue)                          (Dirty white)

CuSO₄ (s) + 5H₂O (l) —— > CuSO₄.5H₂O

                                                      (Blue)

Ans. Na₂CO₃.10H₂O is washing soda, NaHCO₃ is baking soda. NaHCO₃ is an ingredient of antacid. It neutralizes hyper acidity in stomach and gives relief.

Ans. Baking powder is made up of NaHCO₃ and tartaric acid. NaHCO₃, on heating gives CO₂ which makes the cake soft and spongy.

Ans. Zn (s) + 2NaOH —— > Na₂ZnO₂ + H₂

Test: Bring a burning splinter near the gas. If it burns with ‘pop’ sound, the gas liberated is hydrogen.

Zn + H₂SO₄ (dil) —– > ZnSO₄ (aq) + H₂

Hydrogen gas will be evolved by reaction of the same metal with dilute H₂SO₄, strong acid.

Ans. The salt is NaHCO₃, sodium hydrogen carbonate.

NH₃ (g) + CO₂ (g) + NaCl (g) + H₂O (l) —–> NaHCO₃ (s) + NH₄Cl

Uses:

a) It is used as an antacid

b) It is used in soda-acid fire extinguishers.

No salt has pH = 14. NaHCO₃ has pH = 8.4

Ans. a) It contains ions which carry current.

b) H₃O+ ions will decrease when it is diluted

c) Dilute solution has higher pH than concentrated solution.

d. (i) CO₂ gas will be formed.

Na₂CO₃ + 2HCl —– > 2NaCl + H₂O + CO₂  

(ii) Hydrogen gas will be formed.

Zn + 2HCl —- > ZnCl₂ + H₂

Ans. a) pH of our stomach is 2.0 and it is needed for the digestion of proteins in our body.

b) Blood has pH = 7.36 to 7.42 which must be maintained for proper health.

c) pH of soil is determined and suitable chemicals are added so as to make it suitable for growth of crops.

Ans. a) Phenolphthalein will turn pink in soap solution.

b) Chlorine is the by-product of chlor-alkali process which is used in the manufacture of bleaching powder.

c) Universal indicator specifies the various levels of H⁺ ion concentration.

Ans. a) Universal indicator is mixture of indicators used to find pH of solution. It is used to measure levels of H⁺ ion concentration.

b) ‘A’ is basic in nature, ‘B’ is acidic in nature. ‘A’ will have higher pH than ‘B’. it should be greater than 7.

c) Na₂CO₃ is the salt whose pH is more than 7, CuSO₄ is the salt whose pH is less than 7.

Ans. a) pH scale is a scale which is used for measuring hydrogen ion concentration in a solution.

b) pH < 7 for acidic solution, pH > 7 for basic solution, pH = 7 for neutral solution.

Ans. a) Olfactory indicators: They give different smell in acidic and basic medium e.g. onion, clove, vanilla.

b) HNO₃ and H₂SO₄ are strong acids among the given acids.

Ans. a) Mg (s) + 2HCl (dil) —- > MgCl₂ (aq) + H₂ (g)

b) NaOH (aq) + HCl (dil) —– > NaCl (aq) + H₂O (l)

c) CaCO₃ (s) + 2HCl (dil) —– > CaCl₂ (g) + CO₂ (g) + H₂O (l)

Ans. a) Hydrated copper sulphate, CuSO₄.5H₂O is the name and chemical formula of that substance. It loses water of crystallisation on heating and regains these molecules of water on exposure to the atmosphere.

CuSO₄.5H₂O —— > CuSO₄ + 5H₂O

(Blue)                    (Dirty White)

CuSO₄ (s) + 5H₂O (l) —– > CuSO₄.5H₂O

b) Na₂CO₃.10H₂O, washing soda (Sodium carbonate decahydrate) has 10 molecules of water of crystallisation. CaSO₄.2H₂O, gypsum, chemically calcium sulphate dehydrate has 2 molecules of water of crystallisation.

Ans. Burn magnesium ribbon with the help of tongs to form white ash. Dissolve the ash in hot water. Add red litmus which turns blue, showing that MgO is a basic oxide.

2Mg (s) + O₂(g) —- > 2MgO (s)

MgO + H₂O (hot) —- > Mg(OH)₂ (aq)

Heat Sulphur taken in a iron spatula and pass the gas through water. Add blue litmus into it. It will turn red showing SO₂ is an acidic oxide.

S + O₂ —- > SO₂

SO₂ + H₂O —– > H₂SO₃ (Sulphurous acid)

Ans.

Ans. a) ‘X’ is NaHCO₃ (Sodium hydrogen carbonate). ‘Y’ is CO₂ gas, which is used in fire extinguishers.

b) NaHCO₃ (s) + HCl (aq) ——- > NaCl (aq) + H₂O (l) + CO₂ (g)