What volume of `NH_(3)` gas at STP would be needed to prepare 100 ml of 2.5 molal (2.5 m) ammonium hydroxide solution?

Options

A. 5.6 lit
B. 0.056 lit
C. 11.2 lit
D. 0.56 lit

Answer

A

Explanation

Molecular weight of ` NH _ 4 OH = 35 `
Now,
35 g of ` NH _ 4 OH ` is needed to prepare 1 M solution in 1 litre.
` rArr 35 g NH _ 4 O H ` is 1 L solution ` -=` 1 molar solution
` rArr 2.5 xx 35 g NH _ 4 OH ` is 1 L solution `-= 2.5 ` molar solution
` rArr ( 2.5 xx 35 ) /( 10) g NH _ 4 OH ` is 100 L solution ` -= ` 2.5 molar solution
` rArr 8.75 g NH _ 4 OH ` was dissolved
` NH _ 3 + H _ 2O to NH _ 4 OH `
For 35 g ` NH _ 4 OH, NH _ 3 ` needed = 22.4 L at S.T.P
` rArr ` for 8.75 g ` NH _ 4 OH , NH _ 3 ` needed = ` ( 22.4)/(35 ) xx 8.75 L `
` = 5.6 L `