71. Which of the following acids is produced by stomach in human body to help in digestion?
[A] Hydrochloric acid
[B] Sulphuric acid
[C] Nitric acid
[D] Benzoic acid
Show Answer
Correct Answer: A [Hydrochloric acid]
Notes:
Hydrochloric acid produced by the stomach in human body to help in digestion. During indigestion the stomach produces too much acid and this causes pain and irritation.
72. Choose the correct statement:
[A] Tooth enamel is made up of calcium phosphate
[B] Tooth decay starts when the pH of the mouth is lower than 5.5
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
pH change of the mouth is the cause of tooth decay. Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium phosphate is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5.
73. Which of the following is the chemical formula of Carbonic acid?
[A] Ca CO2
[B] H2 CO3
[C] H3 CO4
[D] H CO3
Show Answer
Correct Answer: B [H2 CO3]
Notes:
Carbonic acid is a chemical compound with the chemical formula H2 CO3. Its find its use in many most aerated drinks, such as sodas and soft drinks.
74. What do we call the device which converts the chemical energy of a spontaneous redox reaction into electrical energy?
[A] Galvanic cell
[B] Fuel cell
[C] Electrolytic cell
[D] None of the above
Show Answer
Correct Answer: A [Galvanic cell]
Notes:
A galvanic cell is an electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy. Daniel cell is a kind of Galvanic cell.
75. Where does the oxidation takes place in a Galvanic cell?
[A] Anode
[B] Cathode
[C] Oxidation does not take place
[D] None of the above
Show Answer
Correct Answer: A [Anode]
Notes:
In a galvanic cell, the half-cell in which oxidation takes place is called anode and it has a negative potential with respect to the solution. The other half-cell in which reduction takes place is called cathode and it has a positive potential with respect to the solution.
76. Choose the correct about Lead storage battery:
[A] it is an example of Primary battery
[B] 38% solution of sulphuric acid is used as an electrolyte
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: B [38% solution of sulphuric acid is used as an electrolyte]
Notes:
Lead storage battery is an example of secondary battery. It consists of a lead anode and a grid of lead packed with lead dioxide (PbO2 ) as cathode. A 38% solution of sulphuric acid is used as an electrolyte.
77. Which of the following factors affect the electronic conductance of a metal?
[A] the nature and structure of the metal
[B] the number of valence electrons per atom
[C] temperature
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Electrical conductance through metals is called metallic or electronic conductance and is due to the movement of electrons. The electronic conductance depends on (i) the nature and structure of the metal (ii) the number of valence electrons per atom (iii) temperature (it decreases with increase of temperature).
78. As per Faraday’s Laws of Electrolysis, the amount of chemical reaction which occurs at any electrode during electrolysis proportional to which of the following?
[A] the concentration of electrolyte
[B] length of the electrode
[C] quantity of electricity passed through the electrolyte
[D] All of the above
Show Answer
Correct Answer: C [quantity of electricity passed through the electrolyte]
Notes:
As per Faraday’s 1st Law of Electrolysis, the amount of chemical reaction which occurs at any electrode during electrolysis by a current is proportional to the quantity of electricity passed through the electrolyte (solution or melt).
79. Choose the correct statement about Oxalic acid:
[A] It is weaker than acetic acid
[B] Its condensed chemical formula is HOOCCOOH
[C] Both a and b
[D] None
Show Answer
Correct Answer: B [Its condensed chemical formula is HOOCCOOH]
Notes:
Oxalic acid is an organic compound with the formula C2H2O4. Its condensed formula is HOOCCOOH. Its acid strength is much greater than that of acetic acid.
80. Which gas is produced when Sodium ethanoate is heated with Soda lime?
[A] Methane
[B] Ethane
[C] Acetylene
[D] Ethene
Show Answer
Correct Answer: A [Methane]
Notes:
Sodium salts of carboxylic acids on heating with soda lime (mixture of sodium hydroxide and calcium oxide) give alkanes containing one carbon atom less than the carboxylic acid. This represents deCarboxylation.
