A certain salt X, gives the following results. Its aqueous solution is alkaline to litmus. It swells up to a glassy material Y on strong heating. When conc. H2SO4 is added to a hot solution of X, white crystal of an acid Z separates out. Write equations for all the above reactions and identify X, Y and Z.

The given salt is alkaline to litmus. Therefore, X is a salt of a strong base and a weak acid. Also, when X is strongly heated, it swells to form substance Y. Therefore, X must be borax. When borax is heated, it loses water and swells to form sodium metaborate. When heating is continued, it solidifies to form a glassy material Y. Hence, Y must be a mixture of sodium metaborate and boric anhydride. \[\ce{\underset{Borax (X)}{Na2B4O7} + 7H2O ->[water] \underset{Sodium hydroxide}{2NaOH} + \underset{Orthoboric acid}{4H3BO3}}\] \[\ce{\underset{Borax (X)}{Na2B4O7 * 10H2O} ->[\Delta] \underset{Sodium metaborate}{Na2B4O7} ->[\Delta] \underset{(Glassy material)}{\underset{Boric anhydric}{B2O3}} + 2NaBO2}\] When concentrated acid is added to borax, white crystals of orthoboric acid (Z) are formed. \[\ce{\underset{Borax (X)}{Na2B4O7 * 10H2O} + H2SO4 ->[\Delta] Na2SO4 +\underset{Orthoboric acid}{4H3BO3 + 5H2O}}\]

A Certain Salt X, Gives the Following Results.Its Aqueous Solution is Alkaline to Litmus. It Swells up to a Glassy Material Y On Strong Heating. - Chemistry

Question

A certain salt X, gives the following results.

Its aqueous solution is alkaline to litmus.
It swells up to a glassy material Y on strong heating.
When conc. H₂SO₄ is added to a hot solution of X, white crystal of an acid Z separates out.

Write equations for all the above reactions and identify X, Y and Z.

Answer in Brief

Solution

The given salt is alkaline to litmus. Therefore, X is a salt of a strong base and a weak acid. Also, when X is strongly heated, it swells to form substance Y. Therefore, X must be borax.

When borax is heated, it loses water and swells to form sodium metaborate. When heating is continued, it solidifies to form a glassy material Y. Hence, Y must be a mixture of sodium metaborate and boric anhydride.

$\underset{Borax (X)}{Na_{2} B_{4} O_{7}} + 7 H_{2} O \overset{water}{\to} \underset{Sodium hydroxide}{2 NaOH} + \underset{Orthoboric acid}{4 H_{3} BO_{3}}$

$\underset{Borax (X)}{Na_{2} B_{4} O_{7} \cdot 10 H_{2} O} \overset{Δ}{\to} \underset{Sodium metaborate}{Na_{2} B_{4} O_{7}} \overset{Δ}{\to} \underset{(Glassy material)}{\underset{Boric anhydric}{B_{2} O_{3}}} + 2 NaBO_{2}$

When concentrated acid is added to borax, white crystals of orthoboric acid (Z) are formed.

$\underset{Borax (X)}{Na_{2} B_{4} O_{7} \cdot 10 H_{2} O} + H_{2} SO_{4} \overset{Δ}{\to} Na_{2} SO_{4} + \underset{Orthoboric acid}{4 H_{3} BO_{3} + 5 H_{2} O}$

shaalaa.com

Some Important Compounds of Boron

Is there an error in this question or solution?

Q 11.30 Q 11.29 - (c)Q 11.31 - (i)

Chapter 11: The p-Block Elements - EXERCISES [Page 333]

APPEARS IN

NCERT Chemistry - Part 1 and 2 [English] Class 11

Chapter 11 The p-Block Elements
EXERCISES | Q 11.30 | Page 333

A Certain Salt X, Gives the Following Results.Its Aqueous Solution is Alkaline to Litmus. It Swells up to a Glassy Material Y On Strong Heating. - Chemistry

Advertisements

Advertisements

Question

Solution

APPEARS IN

RELATED QUESTIONS

Select a course

A Certain Salt X, Gives the Following Results.Its Aqueous Solution is Alkaline to Litmus. It Swells up to a Glassy Material Y On Strong Heating. - Chemistry

Advertisements

Advertisements

Question

SolutionShow Solution

APPEARS IN

RELATED QUESTIONS

Select a course

Solution