pH Value

Which of the following solutions has a pH less than 7?
a) Soap solution
b) Baking soda
c) Hydrochloric acid
d) Sodium hydroxide
✅ c) Hydrochloric acid
Explanation: Acids have pH below 7.
(BPSC 2018)

What is the pH of a neutral solution at 25°C?
a) 1
b) 0
c) 14
d) 7
✅ d) 7
Explanation: A neutral solution like pure water has pH = 7.
(BPSC CDPO 2019)

The pH of saliva after a meal becomes:
a) Acidic
b) Basic
c) Neutral
d) More than 14
✅ a) Acidic
Explanation: Food particles and bacterial activity make it slightly acidic.
(BPSC Teacher 2023)

A solution turns blue litmus red. What is its pH likely to be?
a) 8
b) 10
c) 7
d) 4
✅ d) 4
Explanation: Blue litmus turning red shows acidic nature (pH < 7).
(BPSC 2020)

Which of the following is a pH indicator?
a) Vinegar
b) Methyl orange
c) Salt
d) Sugar
✅ b) Methyl orange
Explanation: It changes color in acidic and basic media.
(BPSC 65th Prelims)

Which of the following solutions has the highest pH?
a) Lemon juice
b) Vinegar
c) NaOH
d) HCl
✅ c) NaOH
Explanation: NaOH is a strong base (pH ~14).
(BPSC Assistant 2017)

What is the full form of pH?
a) Potential of hydrogen
b) Power of hydrogen
c) Percent hydrogen
d) Pressure of hydrogen
✅ b) Power of hydrogen
Explanation: pH = potential (power) of hydrogen ion concentration.
(BPSC 64th)

Which of the following has a pH close to 1?
a) Blood
b) Soap solution
c) Lemon juice
d) Battery acid
✅ d) Battery acid
Explanation: Strong acids like H₂SO₄ have very low pH.
(BPSC Teacher 2022)

A pH less than 3 usually indicates:
a) Weak base
b) Weak acid
c) Strong base
d) Strong acid
✅ d) Strong acid
Explanation: pH < 3 denotes strong acidity.
(BPSC 2021)

Which indicator turns pink in basic solution?
a) Litmus
b) Phenolphthalein
c) Methyl orange
d) None
✅ b) Phenolphthalein
Explanation: Phenolphthalein is colorless in acid and pink in base.
(BPSC 2019)

What does a pH value of 0 represent?
a) Very strong acid
b) Weak acid
c) Neutral
d) Very strong base
✅ a) Very strong acid
Explanation: Lower the pH, stronger the acid; 0 is strongest.

Which of these substances has a pH greater than 7?
a) Vinegar
b) Orange juice
c) Ammonia solution
d) Milk
✅ c) Ammonia solution
Explanation: Ammonia is basic, hence pH > 7.

What is the pH range of acids?
a) 0–6.9
b) 7–14
c) Exactly 7
d) 8–14
✅ a) 0–6.9
Explanation: Acids have pH less than 7.

Which common household item has a pH around 10?
a) Lemon juice
b) Bleach
c) Curd
d) Tomato
✅ b) Bleach
Explanation: Bleach is alkaline with a high pH.

Which of these body fluids is slightly basic?
a) Saliva
b) Blood
c) Urine
d) Gastric juice
✅ b) Blood
Explanation: Blood has a pH around 7.35–7.45.

Which of the following substances has pH closest to neutral?
a) Lemon
b) Milk
c) Water
d) Vinegar
✅ c) Water
Explanation: Pure water has a pH of 7.

Which part of the digestive system releases acid?
a) Mouth
b) Esophagus
c) Stomach
d) Intestine
✅ c) Stomach
Explanation: Hydrochloric acid is secreted in the stomach.

pH of gastric juice is approximately:
a) 1–2
b) 6–7
c) 8–9
d) 13–14
✅ a) 1–2
Explanation: It is highly acidic due to HCl.

What is used to treat acidity in the stomach?
a) Hydrochloric acid
b) Sodium chloride
c) Antacid
d) Vinegar
✅ c) Antacid
Explanation: Antacids are mild bases that neutralize excess acid.

If a substance turns red litmus blue, its pH must be:
a) < 7
b) = 7
c) > 7
d) Can’t be determined
✅ c) > 7
Explanation: Red to blue indicates basic character.

Which of these has a pH of about 3?
a) Soap solution
b) Curd
c) Blood
d) Water
✅ b) Curd
Explanation: Curd contains lactic acid—mildly acidic.

Which indicator is used in titration?
a) Methyl orange
b) Litmus
c) Phenolphthalein
d) All of the above
✅ d) All of the above
Explanation: All are used depending on acid-base strength.

An ant bite injects which type of substance?
a) Base
b) Salt
c) Acid
d) Alkali
✅ c) Acid
Explanation: Formic acid is injected, causing pain and irritation.

Tooth decay starts when pH of the mouth falls below:
a) 5.5
b) 6.5
c) 7.0
d) 8.0
✅ a) 5.5
Explanation: Acid attacks enamel below this pH.

Which of these natural indicators is used in labs?
a) Litmus
b) Turmeric
c) China rose
d) All of these
✅ d) All of these
Explanation: All change color with acid or base.

pH paper changes to green in:
a) Strong acid
b) Weak acid
c) Neutral solution
d) Strong base
✅ c) Neutral solution
Explanation: Green color on pH paper means neutral (pH ~7).

Which substance has pH around 2?
a) Lemon juice
b) Soap
c) Blood
d) Milk of magnesia
✅ a) Lemon juice
Explanation: Citric acid gives lemon its acidic pH.

Which of these indicators shows orange in acidic medium?
a) Methyl orange
b) Litmus
c) Phenolphthalein
d) None
✅ a) Methyl orange
Explanation: In acid, methyl orange is red/orange.

pH of solution increases when:
a) H⁺ ions increase
b) OH⁻ ions decrease
c) OH⁻ ions increase
d) Solution is diluted
✅ c) OH⁻ ions increase
Explanation: More OH⁻ = more basic = higher pH.

Strong base has pH closer to:
a) 0
b) 5
c) 7
d) 14
✅ d) 14
Explanation: Strong bases like NaOH have very high pH.

pH scale was developed by:
a) Arrhenius
b) Sorensen
c) Boyle
d) Newton
✅ b) Sorensen
Explanation: Danish chemist S.P.L. Sorensen proposed the pH scale in 1909.

Soil with pH < 6 is treated with:
a) HCl
b) NH₄OH
c) Lime
d) Salt
✅ c) Lime
Explanation: Lime (CaO or Ca(OH)₂) neutralizes acidic soil.

Universal indicator shows violet color for:
a) Weak acid
b) Strong base
c) Strong acid
d) Weak base
✅ b) Strong base
Explanation: Violet/purple indicates very high pH (~13–14).

pH of cold drinks like cola is around:
a) 2.5
b) 5
c) 6.5
d) 8
✅ a) 2.5
Explanation: Carbonic acid lowers the pH of fizzy drinks.

What happens when acid is added to water?
a) Releases OH⁻
b) pH increases
c) pH decreases
d) Water evaporates
✅ c) pH decreases
Explanation: H⁺ ion concentration increases, so pH falls.

Substance with pH 6 is:
a) Strong acid
b) Strong base
c) Weak acid
d) Weak base
✅ c) Weak acid
Explanation: Slightly below 7 = weak acid.

If a solution has equal H⁺ and OH⁻ ions, it is:
a) Acidic
b) Basic
c) Neutral
d) Amphoteric
✅ c) Neutral
Explanation: Equal H⁺ and OH⁻ = neutral pH = 7.

Which of the following will not change color of red litmus?
a) NaOH
b) Lime water
c) Water
d) KOH
✅ c) Water
Explanation: Water is neutral and does not affect litmus.

Which of the following can be used to test soil pH?
a) Thermometer
b) Barometer
c) Litmus paper
d) pH meter
✅ d) pH meter
Explanation: A pH meter gives precise soil pH readings.

The pH value is defined as:
a) log[H⁺]
b) –log[H⁺]
c) log[OH⁻]
d) log[H₂O]
✅ b) –log[H⁺]
Explanation: pH is the negative logarithm of hydrogen ion concentration.

What is the pH of NaOH solution?
a) Around 2
b) Around 5
c) Around 7
d) Around 13–14
✅ d) Around 13–14
Explanation: NaOH is a strong base.

The strength of acids and bases is measured by:
a) Volume
b) Color
c) pH value
d) Boiling point
✅ c) pH value
Explanation: pH value directly reflects H⁺ or OH⁻ concentration.

In pH scale, each step represents change in acidity by:
a) 2x
b) 5x
c) 10x
d) 100x
✅ c) 10x
Explanation: A 1-unit change means 10-fold change in H⁺ ions.

A strong acid has:
a) High H⁺ concentration
b) High OH⁻ concentration
c) Equal ions
d) No ions
✅ a) High H⁺ concentration
Explanation: Strong acids release more H⁺ ions.

Which one is not acidic?
a) Stomach juice
b) Apple juice
c) Baking soda
d) Lemon
✅ c) Baking soda
Explanation: Baking soda is basic (pH ~9).

The color of turmeric in base is:
a) Red
b) Blue
c) Yellow
d) Orange
✅ a) Red
Explanation: Turmeric turns red in basic medium.

The effect of acid rain on aquatic life is due to:
a) High pH
b) Low pH
c) Salt
d) Heavy metals
✅ b) Low pH
Explanation: Acid rain lowers water pH, harming organisms.

Which part of the body maintains pH using buffers?
a) Brain
b) Lungs
c) Blood
d) Skin
✅ c) Blood
Explanation: Blood uses buffers to stay around pH 7.4.

Which acid is present in vinegar?
a) HCl
b) Acetic acid
c) Citric acid
d) Lactic acid
✅ b) Acetic acid
Explanation: Acetic acid gives vinegar its pH (~2.9).

Which common base is used to neutralize bee sting (acidic)?
a) NH₄OH
b) NaOH
c) Baking soda
d) HCl
✅ c) Baking soda
Explanation: Bee sting is acidic and baking soda (NaHCO₃) neutralizes it.