A group of students measured the pH of some substances they found in their homes. Their results are given in the following table: Substance pH Substance pH Apples 3.0 Salt 7.0 Baking soda 8.5 Sugar 7.0 Black coffee 5.0 Toothpaste 9.0 Household ammonia 12.0 Vinegar 3.0 Lemon juice 2.5 Washing soda 11.5 Milk 6.5 (a) What would the students have used to measure the pH? (b) Which solution is the most acidic? (c) Which solution is the most alkaline? (d) Which solutions are neutral? (e) Which solution can be used to treat wasp stings? (f) Which solution can be used to treat bee stings?

(a) Students have used universal indicator paper to measure the pH of substances because universal indicator tells us the strength of an acid and base. (b) pH ∝ 1 [ H + ] ∝ 1 acidic character : pH of lemon juice is 2.5, it contains more concentration of hydrogen ions in it. Hence, it is more acidic. (c) pH ∝ OH - ∝ basic strength : pH of household ammonia is 12. It contains more concentration of hydroxide ions in it. Hence, it is most alkaline. (d) If a solution is having pH 7, then it is said to be a neutral solution because it contains an equal amount of hydrogen ions and hydroxide ions in the solution. Salt and sugar with pH = 7 are neutral. (e) Wasp stings inject an alkaline solution into the skin which causes irritation. Effect of this alkaline solution can be cancelled by rubbing the injected area with vinegar. (f) Bee stings inject methanoic acid into the skin. So baking soda (mild base) can be used for treatment because this base cancels the effect of acid and gives relief.

EASY

Earn 100

What is full form of pH?

Important Questions on Acids, Bases and Salts

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

A solution turns red litmus blue. Its

p H

is likely to be

MEDIUM

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

A teacher provided acetic acid, water, lemon juice, an aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as $3, 12, 4, 8$ and $14$ respectively. Which one of these values is not correct? Write its correct value stating the reason.

MEDIUM

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

A group of students measured the pH of some substances they found in their homes. Their results are given in the following table:

Substance	pH	Substance	pH
Apples	3.0	Salt	7.0
Baking soda	8.5	Sugar	7.0
Black coffee	5.0	Toothpaste	9.0
Household ammonia	12.0	Vinegar	3.0
Lemon juice	2.5	Washing soda	11.5
Milk	6.5

(a) What would the students have used to measure the pH?
(b) Which solution is the most acidic?
(c) Which solution is the most alkaline?
(d) Which solutions are neutral?
(e) Which solution can be used to treat wasp stings?
(f) Which solution can be used to treat bee stings?

MEDIUM

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Define a universal indicator. Mention its one use.

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Answer the following questions:

(a) Explain why the pH in a person's mouth becomes lower after each meal.
(b) What damage could be caused while the pH is low?
(c) How could the person change his eating habits to lessen the chances of suffering from tooth decay?

HARD

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

What is tooth enamel chemically? State the conditions when it starts corroding. What happens when food particles left in the mouth after eating degrade? Why do doctors suggest use of tooth powder/toothpaste to prevent tooth decay?

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Two solutions

X

and

Y

have

p H = 4

and

p H = 8

, respectively. Which solution will give an alkaline reaction and which one acidic?

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

A milkman adds a very small amount of baking soda to fresh milk. Why does this milk take a long time to set as curd?

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

The

pH

of two solutions are

4

and

11

respectively. Indicate their nature.

HARD

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8.

Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Name one animal and one plant whose stings contain formic acid (or methanoic acid).

EASY

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Solution A turns universal indicator blue to purple, whereas solution B turns universal indicator orange to red.
Name any two substances which can give solutions like B.

HARD

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Five solutions

A, B, C, D

and

E

showed

pH

4, 7, 1, 11

and

9

respectively when tested by universal indicator. Which solution is
(i) Neutral (ii) Strongly acidic (iii) Strongly alkaline (iv) Weakly alkaline (v) Weakly acidic. Arrange the

pH

in increasing order of

H^{+}

ion concentration.

HARD

Science>Chemistry>Acids, Bases and Salts>Strength of Acids and Bases

Here are some results of solutions tested with universal indicator paper:
Sulphuric acid : Red
Metal polish : Dark blue
Washing-up liquid : Yellow
Milk of magnesia : Light blue
Oven cleaner : Purple Pink
Car battery acid : Pink
Arrange the solutions in order of their increasing pH values(starting with the one with the lowest