O Level Chemistry: Preparation of Salts

15 Oct

Posted by: sean in: Chemistry Notes & Tips

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Question on “Preparation of Salts” for discussion:

Question:
Which pair of substances is most suitable for the preparation of copper(II) sulphate?
A. Aqueous copper(II) nitrate and aqueous sodium sulphate
B. Copper(II) carbonate and dilute sulphuric acid
C. Copper and dilute sulphuric acid
D. Copper(II) oxide and ammonium sulphate

Takers??

PS: Leave your answers in the “Comments” section below.

Rgds
Sean

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14 Responses

cherie
16|Oct|2007 1

my guess is A as both are soluble salts hahah im not that sure too.

what’s the correct answer?:D

Reply
h3llsmokes
16|Oct|2007 2

my ans is C

A and D will have no reaction as A is both salts and they wont react. For D, copper oxide is a base and wont react with ammonium sulphate
B is copper with dilute sulphuric acid. copper would not react with dilut sulphuric acid as copper is less reactive than hydrogen. Hence the ans is C

Reply
illuminate-x
16|Oct|2007 3

Copper (II) sulphate is is soluble which means an insoluble metal/base/carbonate and an acid is needed to prepare it… so my answer would be B. It can’t be C because copper is too unreactive to react with H2SO4

Reply
LinwooD
16|Oct|2007 4

I dont think it’s A, because Copper is less reactive than Sodium, so Sodium is not replaced.

B – no, because copper (II) carbonate is insoluble.

C – Copper will react with sulphuric acid to form Copper (II) Sulphate and hydrogen gas.

D – somehow it’s not the right answer and i think there’s no ammonium oxide? or maybe there is, or maybe it will form something else, but i think D is not the most suitable if compared to the easier method in C.

Therefore, my answer is C.

please answer ASAP, o level is so around the corner.

Reply
FluffySnow
16|Oct|2007 5

The answer is B.

C is definitely out, since copper is unreactive and does not react with dilute acids.

Copper (II) carbonate is insoluble. Hence, it is added in excess to ensure that all of the acid is used up (to form Copper (II) Sulphate). It is then filtered off from the mixture, leaving behind pure, aqueous CuSO4.

and then u heat it to saturation, crystallize and so forth. : )

Reply
Anonymous
17|Oct|2007 6

I thought copper carbonate is not insoluble?!

Reply
lijun(:
17|Oct|2007 7

B.

CuSO4 is soluble in water, hence can be obtained by B.
CuCO3(s)+H2SO4(aq) -> CuSO4(aq)+CO2(g)+H2O(l)

A and D are not possible, since it will not undergo ions exchange, as all the reactants and products are aqueous.

C is also not possible, since Cu is too unreactive, and will not react with acid. it is also because it is below Hydrogen in the reactivity series, hence cannot displace H+ ions.

Reply
FluffySnow
18|Oct|2007 8

anonymous: the only soluble carbonates are group 1 carbonates and ammonium carbonate.

Reply
Spirit-Breaker
18|Oct|2007 9

B
H2 SO4 + CuCO3 — CuSO4 + H2O + CO2
Is it true?

Reply
ruth
20|Oct|2007 10

Weeeell, A isn’t wrong per say cause you will get copper(II) sulphate. Yes, they are both soluble salts which means that you’ll find that they deionise in water to form ions(duh, lol).
Thus, some of the ions will bond to form copper(II) sulphate but it isn’t a very effective method ^ ^
For the pure copper and acid reaction, there won’t be any reaction at all since copper’s less reactive than hydrogen and won’t be able to displace it.
And yeah well, the answer should be copper carbonate and the acid. See right, the rule of thumb is that since copper is low down in the reactivity series, it doesn’t like staying as a salt and will decompose easily. Thus when you react it with acid, it’ll easily form copper(II) sulphate, water and carbon dioxide.
The last two are just bases so, no reaction as lots of you have said(:

AND AND copper carbonate is insoluble. The only soluble carbonates are sodium carbonate, potassium carbonate and ammonium carbonate.

Reply
Sean Chua
20|Oct|2007 11

Ruth is right!

Copper being a very unreactive metal will tends to form very unstable (thus reactive)compounds with other element(s).

Copper (II) carbonate is not a very stable compound of Cu and thus tends to react with the H2SO4 based on the word equation below.

Answer should be B.

PS: The only soluble carbonates are SPA – Sodium, Potassium and Ammonium carbonates.

Sean
SimpleChemConcepts
“Learning Experience with A Difference”

Copper(II) carbonate + sulphuric acid ==> copper(II) sulphate + water + carbon dioxide

Reply
Anonymous
23|Oct|2007 12

It A la….u all know y? because in order to produce a salt both substance must be in aqueous form…..

Reply
dreamsforeva
01|Nov|2007 13

its B!

C is out cos copper is unreactive.
as for A, both the products are aq which makes it difficult to seperate them.

For B, sulphuric acid and excess of insoluable copper carbonate to ensue that all of the acid is used up.

since the excess copper carbonate is insoluable, it can easily be filtered out.
the pure filtrate is then evaporated to dryness to obtan pure cuso4 crystals.

there!

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yi en
05|May|2009 14

Copper sulphate is soluble. So you can either prepare it using titration or crystallisation. Crystallisation is easier and it has lesser steps than titration.
A is wrong as the two salts would not react at all.
B is correct
C is wrong as copper is an unreactive metal and the reaction would not occur
D is wrong as the two salts would not react.

So B is correct right?

Reply