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LC Chemistry Experiments > Preparation of ethyne > Flashcards

Preparation of ethyne Flashcards

1
Q

draw a diagram of the set up of this exp.

A

water
Cac2
CONICAL FLASK HOLDING CAC2 MUST BE CLEARLY STOPPERED
acidified copper sulphate
ethyne
basin of water

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2
Q

what is CaC2

A

a grey black solid

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3
Q

how do we collect the ethyne

A

over water

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4
Q

what happens when water is dropped on calcium carbide

A

fizzing

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5
Q

why does fizzing occur when water is dropped on calcium carbide

A

ethyne gas is produced

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6
Q

what colour does the calcium carbide change to after water is added

A

white solid

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7
Q

what is the white solid formed when water is added to CaC2

A

calcium hydroxide

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8
Q

why does the flask get warm during the reaction?

A

an exothermic reaction is occurring

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9
Q

why do we need to keep naked flames away from this exp

A

Ethyne forms an explosive mixture with air

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10
Q

why do we use a glass jar instead of a test tube?

A

glass is thicker and less likely to shatter

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11
Q

what does the gas produced in the first flask need to be bubbled through?

A

acidified copper sulphate solution

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12
Q

why do we bubble the gas through acidified copper sulphate solution

A

to remove impurities

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13
Q

what impurities are found in the product

A

hydrogen sulphide
ammonia
phosphine

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14
Q

what impurities are in calcium carbide

A

calcium phosphide
calcium nitride
calcium sulphide

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15
Q

why do we discard the first 2 test tubes of gas collected

A

they contain mainly displaced air and ethyne

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16
Q

why doe we fill a gas jar with the gas

A

to test the gas for combustion

17
Q

what colour is ethyne

A

colourless

18
Q

what does ethyne smell like

A

sweet

19
Q

is ethyne soluble in water

A

no
ethyne is non polar
water is polar
ethyne cannot form hydrogen bonds with water

20
Q

how do we test for the combustion of ethyne

A

hold a lighted wax taper at the mouth of the gas jar note soot produced

21
Q

why is soot produced when ethyne is combusted

A

soot= solid carbon due to the incomplete combustion of ethyne as not enough oxygen is available to ensure complete combustion

22
Q

write a balanced equation for the combustion of ethyne

A

C2H2 + 2.5O2 —-> 2CO2 + H2O

23
Q

write the balanced equation for this reaction

A

CaC2 + 2H2O —–> Ca(OH)2 + C2H2

24
Q

what type of reaction is this

A

substitution reaction

LC Chemistry Experiments (11 decks)

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