Blue litmus solution is added to two test ...

CBSE Class 10 Science 2019 Delhi Set 1

Question : 22 of 28

Marks: +1, -0

Blue litmus solution is added to two test tubes

A

and

B

containing dilute

\mathrm{HCl}

and

\mathrm{NaOH}

solution respectively. In which test tube a colour change will be observed? State the colour change and give its reason.

What is observed when

2\,\text{mL}

of dilute hydrochloric acid is added to

1\,\text{g}

of sodium carbonate taken in a clean and dry test tube? Write chemical equation for the reaction involved.

Solution:

Test tube A will show colour change because acids turn blue litmus to red. So the final colour of test tube would be red.

A brisk effervescence would be observed if

\mathrm{HCl}

is added to

\mathrm{Na}_2\,\mathrm{CO}_3

due to the evolution of

\mathrm{CO}_2

gas.

\mathrm{Na}_2\mathrm{CO}_3 + \mathrm{HCl} \rightarrow \mathrm{NaCl} + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2

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