Class 7 Chemistry Worksheet on Chapter 5 Acids, Bases and Salts ... - Free Printable

Let's solve each question from the Chemistry Worksheet Class 7 on Chapter 5: Acids, Bases and Salts - Set 2, along with explanations.

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Q1. Window cleaner contains

(a) Magnesium hydroxide
(b) Ammonium hydroxide
(c) Calcium hydroxide
(d) None of the above

✔ Answer: (b) Ammonium hydroxide

🔹 Explanation:
Ammonium hydroxide (NH₄OH) is a weak base commonly used in window cleaners because it helps dissolve grease and dirt. It is effective at cleaning glass without leaving streaks.

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Q2. Tamarind, grapes and unripe mangoes contain

(a) Tartaric acid
(b) Citric acid
(c) Ascorbic acid
(d) Both (b) and (c)

✔ Answer: (d) Both (b) and (c)

🔹 Explanation:
- Citric acid is found in citrus fruits like lemons, oranges, and also in tamarind and grapes.
- Ascorbic acid (Vitamin C) is present in many fruits including unripe mangoes, tamarind, and grapes.
- So both citric acid and ascorbic acid are present in these fruits.

> Note: While tartaric acid is present in grapes, it’s not common in tamarind or unripe mangoes — so option (a) alone is incorrect.

Thus, correct answer is (d).

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Q3. What is the chemical name of baking soda?

(a) Potassium hydrogen carbonate
(b) Magnesium hydrogen carbonate
(c) Sodium hydrogen carbonate
(d) None of the above

✔ Answer: (c) Sodium hydrogen carbonate

🔹 Explanation:
Baking soda is chemically known as Sodium hydrogen carbonate (NaHCO₃). It is used in baking as a leavening agent and in household cleaning.

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Q4. What is the effect of aerated drinks or soda water on the china rose indicator?

(a) Light pink to green
(b) Light pink to magenta
(c) Green to light pink
(d) Magenta to light pink

✔ Answer: (a) Light pink to green

🔹 Explanation:
China rose indicator is a natural indicator that changes color based on pH:
- In acidic solutions → turns green
- In basic solutions → turns magenta
- In neutral → light pink

Aerated drinks (like soda water) contain dissolved CO₂, which forms carbonic acid (H₂CO₃) — making the solution acidic.

So, when added to china rose indicator, it turns light pink → green.

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Q5. Excessive use of fertilisers in the land makes the land

(a) Acidic
(b) Alkaline
(c) Neutral
(d) All of the above

✔ Answer: (a) Acidic

🔹 Explanation:
Many chemical fertilizers (especially nitrogen-based ones like ammonium nitrate or urea) increase the acidity of soil over time due to nitrification processes. This leads to soil acidification, harming plant growth and microbial activity.

> While some fertilizers may make soil alkaline, excessive use generally results in acidic conditions due to leaching and metabolic byproducts.

So, best answer is (a) Acidic.

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Q6. State true or false.

Acid turns blue litmus red.

✔ Answer: True

🔹 Explanation:
This is a fundamental property of acids:
- Acids turn blue litmus paper red.
- Bases turn red litmus paper blue.

So, this statement is True.

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Q7. State true or false.

Acetic acid is present in vinegar, whereas citrus fruits contain citric acid.

✔ Answer: True

🔹 Explanation:
- Vinegar is made by fermenting ethanol into acetic acid (CH₃COOH).
- Citrus fruits (like lemon, orange, grapefruit) contain citric acid, which gives them their sour taste.

So, this statement is True.

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✔ Final Answers Summary:

| Q.No | Answer |
|------|--------|
| Q1 | (b) Ammonium hydroxide |
| Q2 | (d) Both (b) and (c) |
| Q3 | (c) Sodium hydrogen carbonate |
| Q4 | (a) Light pink to green |
| Q5 | (a) Acidic |
| Q6 | True |
| Q7 | True |

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