Sunday, 21 May 2017

CBSE Class 10 Chemistry - CH2 Acids and Bases - Very Short Questions and Answers (#cbsenotes)

Acids and Bases  

CBSE Class 10 Chemistry - CH2 Acids and Bases - Very Short Questions and Answers (#cbsenotes)

Very Short Questions and Answers
Class 10 Science - Chemistry

Q1: What is an acid?

Answer: Acid is a compound which yields hydrogen ions (H⁺) or Hydronium (H₃O⁺) ions , when dissolved in water.

Q2: What is the pH value of acids?

Answer: Less than 7 (i.e. 0 to < 7)

Q3: What is the taste of acids?

Answer: Sour

Q4: What happens to blue litmus paper when it comes in contact with acid solution?

Answer: It turns into red.

Q5: On the basis of origin, how acids are classified as?

Answer: Organic acids and Mineral acids.

Q6: How acids are classified as on the basis of strength?

Answer: Strong acids and Weak Acids

Q7: Give two examples of organic acids.

Answer: acetic acid present in vinegar and oxalic acid present in tomato.

Q8: Give two examples of mineral acids.

Answer: Sulphuric Acid (H₂SO₄) and Hydrochloric acid (HCl)

Q9: On the basis of their concentration, how are acids classified as?

Answer: Dilute acids and Concentrated acids.

Q10: In which acid (dilute or concentrated), hydrogen ions (H⁺) is maximum?

Answer:  Concentrated acid.

Q11: How does a strong acid differ from a concentrated acid?

Answer: The strength of an acid depends upon its dissociation power whereas concentration depends on water content in the acid.

Q12: On the basis of number of hydrogen ion, how are acids classified?

Monoprotic acid
Diprotic acid
Triprotic acid
Polyprotic acid

Q13: Give examples of two weak acids.

Answer: Acetic acid (CH₃COOH) and Carbonic acid (H₂CO₃)

Q14: Is mixing of water and acid exothermic or endothermic process.

Answer: Mixing of water and acid is a highly exothermic process.

Q15: Name the ions produced by bases when in aqueous form?

Answer: Hydroxide ions (OH⁻)

Q16: What is the taste of bases?

Answer: Bitter taste

Q17: What is the action of red litmus paper on bases?

Answer: It turns blue.

Q18: How does it feel when we touch bases?

Answer: Soapy or Slippery feel

Q19: Give two examples of strong bases.

Answer: Sodium hydorxide (NaOH) and Potassium hydroxide (KOH)

Q20: Give an example of weak base.

Answer: Ammonium hydroxide (NH₄OH)

Q21: What are alkalis?

Answer: Water soluble bases are called alkalies.

Q22: What is the pH value of distilled water?

Answer: 7 (neutral)

Q23: What is the pH range of normal human being?

Answer: pH 7 to 7.8

Q24: What is a salt?

Answer: When an acid and base combine in a neutralization reaction, it forms a salt and water.

Q25: Give an example neutralization reaction forming a neutral salt.

Answer: NaOH + HCl --------> NaCl + H₂O

Q26: Give an example neutralization reaction forming a acidic salt.

Answer: HCl + NH₄OH --------> NH₄Cl + H₂O

Q27: Give an example neutralization reaction forming a basic salt.

Answer: CH₃COOH + NaOH--------> CH₃COONa + H₂O

Q28: What is the colour of methyl orange in acidic medium?

Answer: Pink

Q29: What is the colour of methyl orange in basic medium?

Answer: Orange

Q30: What is colour of Phenolphthalein in acidic medium?

Answer: Colourless

Q31: What is colour of Phenolphthalein in basic medium?

Answer: Pink

Q32: What are olfactory indicators?

Answer: Those indicators whose odour changes in acidic or basic medium are called olfactory indicators. e.g. vanilla and onion.

Q33: What happens to smell of onion in bases and in acids?

Answer: Smell of onion diminishes in a base and remains as it is in an acid.

Q34: What is the reaction or turmeric on acids and bases?

Answer: In acids, yellow colour of turmeric remains yellow. In bases, yellow colour of turmeric turns red.

Q35: Give two examples of natural indicators?

Answer: Litmus and Turmeric.

Q36: Name the gas evolved when metals react with acids?

Answer: Hydrogen gas.

Q37: What is brine?

Answer: NaCl dissolved in water.

Q38: What are the products of Chlor Alkali process?

Answer: Chlorine (Cl₂), Hydrogen (H₂) and Sodium hydroxide (NaOH)

Q38: Name the chemical formula of bleaching powder?

Answer: Sodium hydrogen carbonate (NaHCO₃)

Q39: Name the chemical formula of Washing soda.

Answer: Sodium carbonate Na₂CO₃.10H₂O

Q40: Name the chemical formula of Plaster of Paris.

Answer: Calcium sulphate hemihydrate CaSO₄.½H₂O

Q41: When the rain water is said to be acid rain?

Answer: Rain water with a pH less than 5.6 is called acid rain.

Q42: Name the acid contained by nettle leaves.

Answer: Methanoic acid

Q43: Name a hydrated salt.

Answer: CuSO₄.5H₂O

Q44: Name two non-hydrated crystalline salts.

Answer: Sodium chloride (NaCl) and Potassium Chloride (KCl)

Q45: What is Water of crystallisation?

Answer: It is the fixed number of water molecules present in one formula unit of a salt.

Q46: Name the effervesence evolved when a metal carbonate is heated?

Answer: CO₂

Q47: Name the group of substances, used to neutralise the excess acid in our stomach.

Answer: Mild bases like baking soda, milk of magnesia

Q48: Name the components present in baking powder.

Answer: sodium bicarbonate  and tartaric acid.

Q49: Fresh milk has a pH of 6. Write the change in pH when it turns into curd.

Answer: It decreases further (less than 6) and becomes more acidic due to formation of lactic acid.

Q50: Name the acid produced by our stomach.

Answer: HCl

Q51: Why does distilled water has pH value of 7?

Answer: In pure water, water molecules dissociates into equal amounts of  H⁺ and OH⁻ ions thus maintaining the neutrality.

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