Preparation of ethyne Flashcards
draw a diagram of the set up of this exp.
water
Cac2
CONICAL FLASK HOLDING CAC2 MUST BE CLEARLY STOPPERED
acidified copper sulphate
ethyne
basin of water
what is CaC2
a grey black solid
how do we collect the ethyne
over water
what happens when water is dropped on calcium carbide
fizzing
why does fizzing occur when water is dropped on calcium carbide
ethyne gas is produced
what colour does the calcium carbide change to after water is added
white solid
what is the white solid formed when water is added to CaC2
calcium hydroxide
why does the flask get warm during the reaction?
an exothermic reaction is occurring
why do we need to keep naked flames away from this exp
Ethyne forms an explosive mixture with air
why do we use a glass jar instead of a test tube?
glass is thicker and less likely to shatter
what does the gas produced in the first flask need to be bubbled through?
acidified copper sulphate solution
why do we bubble the gas through acidified copper sulphate solution
to remove impurities
what impurities are found in the product
hydrogen sulphide
ammonia
phosphine
what impurities are in calcium carbide
calcium phosphide
calcium nitride
calcium sulphide
why do we discard the first 2 test tubes of gas collected
they contain mainly displaced air and ethyne
why doe we fill a gas jar with the gas
to test the gas for combustion
what colour is ethyne
colourless
what does ethyne smell like
sweet
is ethyne soluble in water
no
ethyne is non polar
water is polar
ethyne cannot form hydrogen bonds with water
how do we test for the combustion of ethyne
hold a lighted wax taper at the mouth of the gas jar note soot produced
why is soot produced when ethyne is combusted
soot= solid carbon due to the incomplete combustion of ethyne as not enough oxygen is available to ensure complete combustion
write a balanced equation for the combustion of ethyne
C2H2 + 2.5O2 —-> 2CO2 + H2O
write the balanced equation for this reaction
CaC2 + 2H2O —–> Ca(OH)2 + C2H2
what type of reaction is this
substitution reaction