The drain cleaner, Drainex contains small bits of aluminum which react with caustic soda to produce dihydrogen. - Chemistry

Numerical

The drain cleaner, Drainex contains small bits of aluminum which react with caustic soda to produce dihydrogen. What volume of dihydrogen at 20 °C and one bar will be released when 0.15g of aluminum reacts?

Solution

The chemical equation for the reaction is

$\ce{\underset{\ce{2 x 27 g}}{2 Al} + 2 NaOH + 2H2O -> 2NaAlO2 + \underset{\ce{3 x 22400 mL}}{3H2}}$

At STP (273.15 K and 1 atm), 54 g (2 × 27 g) of Al gives 3 × 22400 mL of H2..

∴ 0.15 g Al gives (3xx22400xx0.15)/54mL of H2 i.e., 186.67 mL of H2.

= 186.7 mL

S.T.P condition "V"_1 = 186.7 mL , "V"_2 = ?

"P"_1 = 1.013 bar ,   "P"_2 = 1 bar

"T"_1 = 0 + 273 = 273 K,  "T"_2 = 20 + 273 = 293 K

Accourding to gas equation

("P"_1"V"_1)/"T"_1 = ("P"_2"V"_2)/"T"_2   or

"V"_2 = ("P"_1"V"_1"T"_2)/("P"_2"T"_1)

"V"_2 = (1.013 " bar" xx 186.7 " mL" xx 293" K")/ (1 "bar" xx 273 " K")

= 203 mL

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Chapter 5: States of Matter - EXERCISES [Page 158]

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NCERT Chemistry Part 1 and 2 Class 11
Chapter 5 States of Matter
EXERCISES | Q 5.6 | Page 158

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