CBSE Class 10 Science 2018 Solved Paper

Question : 7 of 27

Marks: +1, -0

2 {\ml}

of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid?
The

{\pH}

of a salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses.

Solution:

{\Zn}+2 {\NaOH} → { {\Na}_2 {\ZnO}_2}↙{\text "Sodium zincate"}+ {{\H}_2}↙{\text "Hydrogen gas"}

the hydrogen gas, it burns with the pop sound and the candle will go off.
When zinc metal reacts with dilute solution of strong acid then zinc chloride and hydrogen gas will be formed.

{\Zn}( {\s})+ {\HCl} {\;\text "(aq.) "\;} → { {\ZnCl}_2(\aq.) }↙{\text "Zinc chloride"}+ {\H}_2(\g)

OR
The salt commonly used to make tasty and crispy pakoras is baking soda i.e., sodium hydrogen carbonate

( {\NaHCO}_3)

.
Chemical equation for its formation :

{\NaCl}+ {\H}_2 {\O}+ {\CO}_2+ {\NH}_3 →\; {\NH}_4 {\Cl} +\; {\NaHCO}_3

Uses of Baking soda :
(i) It is used in fire extinguisher.
(ii) It is also used as ingredient of antacid.

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