to prepare ethyne and examine its properties

why is H2O added drop wise

to maintain an even evolution of ethyne

physical appearance of calcium carbide

off white, grey, dirty solid

whats observed

milky, bubbling, heating, white powder

why is ethyne bubbled in acidified copper sulfate 

to purify it 

what substance is left behind in the buchner flask

calcium hydroxide

impurities if ethyne mixed

hydrogen sulfide, phosphine, ammonia

ethyne flame

sooty, dark

reaction equation

CaC2 + 2H2O - > C2H2 +Ca(OH)2

combustion reaction

C2H5 + 21/2O2 - > H2O +2CO2

procedure

set up apparatus like in diagram. add calcium carbideto flask. using a dropping funnel add water slowly to the flask to maintain an even evolution of ethyne. the reaction mixture turns milky, bubbling occurs and the flask gets hot - exothermic reaction. ethyne is formed and travels along delivery tube. bubbled through acidified copper sulfate to purify it. collect 5 test tubes of gas. dismantle the apparatus and dispose of the reaction mixture in the buchner flask to prevent more ethyne gas being produced, as it is explosive in air. perfom tests on test tubes. observe appearance colourless, sweetish smell. place lighted taper over the mouth, a sooty flame. test for unsaturated compounds.