Question

The drain cleaner Drainex contains small bits of aluminium which react with caustic soda to produce hydrogen What volume of hydrogen at `20^(@)C` aand one bar will be released when `0.15 g` of aluminium reacts ? .

Answer 1

Step I. Calculation of the volume of hydrogen released under N.T.P. conditions
The chemical equation for the reaction is :
`underset(2xx27=54g)(2Al+2NaOH)+2H_(2)O+2H_(2)Orarrunderset("Sod. meta aluminate")(2NaAlO_(2))+underset(3xx22400 mL)(3H_(2))`
`54g` of Al at N.T.P release `H_(2)` gas ` = 3 xx 22400 mL`
`0.15 g` of Al at N.T.P. release `H_(2)` gas `((3 xx 22400 mL) xx (0.15 g))/((54 g)) = 186.7 mL`.
Step II Calculating of volume of hydrogen released at `20^(@)C` and 1 bar pressure.
`{:("N.T.P. Conditions",,"Given Conditions"),(V_(1)=186.67mL,,V_(2)=?),(P_(1)=1.013"bar",,P_(2)=1"bar"),(T_(1)=0+273=273K,,T_(2)=20+273=293K):}`
According 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))`
By substituting the values, `V_(2) = ((1.013 "bar" ) xx (186.7 mL) xx (293 K))/((1 "bar") xx (273 K)) = 203 mL`.