Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q85 (NDA-II/2013) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Two reactants in a flask produce bubbles of gas; it turns lime water into milky. The reactants in the flask are

Result
Your answer: —  Â·  Correct: B
Explanation

The observation of gas bubbles that turn lime water milky is the standard chemical test for carbon dioxide (CO2) [1]. When carbon dioxide reacts with lime water (calcium hydroxide), it forms a white precipitate of calcium carbonate, which gives the solution a milky appearance [3]. According to the general chemical principle, metal carbonates react with acids to produce a salt, water, and carbon dioxide gas [4]. In the given options, magnesium carbonate reacting with hydrochloric acid follows this pattern: MgCO3 + 2HCl → MgCl2 + H2O + CO2. In contrast, the reaction between zinc and hydrochloric acid produces hydrogen gas, which does not turn lime water milky. Magnesium nitrate and magnesium sulphate do not react with hydrochloric acid to produce carbon dioxide gas, making option 2 the only scientifically accurate choice.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > Activity 5.4: Let us experiment > p. 61
  2. [3] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.5 > p. 21
  3. [4] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.5 > p. 20
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
74%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

CDS-II · 2018 · Q1 Relevance score: 8.46

Two reactants in a flask at room temperature are producing bubbles of a gas that turn limewater milky. The reactants could be

CDS-II · 2012 · Q22 Relevance score: 3.68

The gas which turns limewater milky is

CDS-I · 2020 · Q102 Relevance score: 2.50

When air is blown from the mouth into a test tube containing limewater, the limewater turns milky. This is due to the presence of

CDS-II · 2014 · Q25 Relevance score: 0.98

When carbon dioxide is passed through lime water, the solution turns milky, but, on prolonged passage, the solution turns clear. This is because

CDS-II · 2018 · Q3 Relevance score: -1.09

Reaction between which of the following two reactants will produce hydrogen gas?