Class 10 Chemistry Chapter Acids Bases and Salts
Important Multiple Choice questions (MCQs)and answers:
1. Which one of the following substances cannot be classified as Arrhenius base?
A. NaOH
B. KOH
C.NH4OH
D.NH3
Ans
D.NH3
Reason
According to Arrhenius’s concept “a base is a substance that ionizes in water to produce OH- ions.
Arrhenius’s theory is only applicable to aqueous solutions and does not explain the compounds like NH3 is basic but there is no hydroxide in this compound.
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2. Which one of the following substances cannot be classified as Arrhenius acid?
A. H2SO4
B. HCl
C. CO2
D. All of these
Ans
C. CO2
Reason
According to Arrhenius’s concept “an acid is a substance that ionizes in water to produce H+ ions.
Arrhenius’s theory is only applicable to aqueous solutions and does not explain that compounds like CO2, SO2 are acidic but there is no hydrogen in these compounds.
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3. Which one of the given is correct?
A. Acids turns blue litmus paper red
B. Acids turns red litmus paper blue
C. Acids produces hydroxide ions in an aqueous solution
D. None of these
Ans
A. Acids turns blue litmus paper red
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4. A strong acid is identified as it is:
A. Completely ionized in water
B. Partially ionized in water
C. Do not get ionized in water
D. Both A & B
Ans
A.Completely ionized in water
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5. Which of the given is used as an antacid?
A. Sodium bicarbonate
B. Calcium carbonate
C. Magnesium oxide
D. None the these
Ans
- Sodium bicarbonate
Sodium bicarbonate reduces stomach acid so it is used as an antacid
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6. If a substance has a pH value of 4?
A. The substance is a base
B. The substance is an acid
C. Neutral substance
D. None of these
Ans
B. The substance is an acid
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7. Chemists use a number scale to describe the concentration of hydrogen ions in a solution. The range of pH scale is from
A. 0 to 10
B. 7 to 10
C. 0 to 14
D. 7 to 14
Ans
C. 0 to 14
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8. Choose Lewis base:
A. BF3
B. HCl
C. AlCl3
D. F-
Ans
D. F-
Reason:
F- has a lone pair of electrons and is an electron-rich specie so it is an electron-pair donor.
Therefore, F- is a lewis base.
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9. Which one is Lewis acid:
A.CN-
B.NH3
C. H2O
D. BF3
Ans
D. BF3
Reason:
Boron in BF3 has 3 valence electrons and after sharing with fluorine it has 6 valence electrons so its octet is incomplete. Therefore, it needs an electron pair to complete its octet (8 valence electrons).
Hence, BF3 is an electron pair acceptor or Lewis acid.
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10. Which element is always present in Arrhenius acid?
A. Carbon
B. Nitrogen
C. Hydrogen
D. All of these
Ans
- Hydrogen
Reason
According to Arrhenius concept “an acid is a substance that ionizes in water to produce H+ ions.
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11. Methyl red color in acidic solution is
A. Yellow
B. Pink
C. Red
D. Orange
Ans
C.Red
Methyl red is an acid-base indicator that gives red colour in acidic and yellow colour in basic solution.
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12. Soda ash chemical formula is
A. NaHCO₃
B. NaNO₃, 9H₂O
C. Na₂CO₃
D. Na₂SO4
Ans
- Na₂CO₃
Soda ash is also known as sodium carbonate (Na₂CO₃)
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13. What is the color of phenolphthalein in a basic medium?
A. Pink
B. Orange
C. Purple
D. Yellow
Ans
- Pink
Phenolphthalein is an acid-base indicator that is colourless in acidic and gives pink colour in basic medium.
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14. Phenolphthalein an acid-base indicator color in basic solution is ____but in acid it is ______.
A. Pink, Colorless
B. Yellow, Pink
C. Colorless, Orange
D. Blue, Red
Ans
A. Pink, Colorless
Phenolphthalein indicator is colorless in acidic solution and shows pink color in basic solution.
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15. pH scale of a neutral solution is
A. 14
B. 7
C. 10
D. 12
Ans
B. 7
The pH scale measures how acidic or basic a solution is.
pH below 7 indicates the solution is acidic
pH above7 indicates the solution is basic
pH 7 indicates a neutral solution
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