Chem qns

TYING SG

hey!! please help! Tmr chem test and still not know how to do.
Which of the following does not react with dilute sulphuric acid?
A. Magnesium hydroxide
B. Magnesium metal
C. Magnesium nitrate
D. Magensium Oxide

Bi(2)O(3)(s) + 3C(s) --> 2Bi(s) + 3CO(g)

How many moles of carbon are required to remove the oxygen from 2 moles of Bi(2)O(3)?

What is the maximum mass of the element that could be manufactured using thirty-six tonnes of carbon?

Thanks a lo!

OasisBlue SG

if i am not wrong its C. Magnesium nitrate

second qns should be 6

i'm not sure bout the 3rd qns... sorry

TYING SG

Hey thanks a lot! it did help me. But would you mind if u explain the qn??

Embarassed and thanks again.

dbowie SG

Bi(2)O(3)(s) + 3C(s) --> 2Bi(s) + 3CO(g)
36ton-3C
1mol-12ton
12ton x 2 = 24ton if u are asking for Bi.

OasisBlue SG

hmmm magnesium nitrate is a salt that's why it doesn't react.

Bi(2)O(3)(s) + 3C(s) --> 2Bi(s) + 3CO(g)

in this equation, 1 mole of bi2o3 requires 3 moles of C

thats why 2 moles of it require 6 moles of C

that's what my teacher taught.

sorry if it's wrong Smile

VeNgEaNcE.oF.rAiN SG

If I am not wrong OasisBlue's first and second answer is correct while the thrid... I think is 24 tonnes.

3rd Question:

Bi[2]O[3] + 3C --> 2Bi + 3CO

Since 3 moles of Carbon is used in the equation. We may use a direct proportion method.

3 moles C --> 2 moles Bi
36 tonnes C --> 24 tonnes Bi

For the 1st question:

Magnesium Nitrate does not react as it is already a salt[an stable ionic compound].

Magnesium metal, Magnesium oxide and Magnesium oxide do react to form a salt.

For the 2nd question:

Direct proportion method

1 mole of Bi[2]O[3] --> 3 mole C
Therefore,
2mole of Bi[2]O[3] --> 6 mole C

I think the answers are correct though I am not sure... Good Luck... Byebye Razz

dbowie SG

Bi(2)O(3)(s) + 3C(s) --> 2Bi(s) + 3CO(g)
to remove ,in other words is to make it react
since 1 mol of Bi2O3 reacts with 3 mol of C,
2 mol of Bi2O3 should react with 6mols of C.

Evo4eva SG

Errmm...so what is the ans for the third part ar?..haha..24???...
and anyone got any gut feeling that a certain topic is sure to come out tml? Embarassed ...haha...other than organic chem

davidche SG

all wrong explaination for qn 1. Try again.

LordIcarus SG

first one. answer is C.
cause:
acid + carbonate - Salt + carbon dioxide + water.
acid + metal - salt + hydrogen.
acid + base - salt and water.

I believe metal nitrate is a salt?

wishboy SG

ur explanation confirm right meh? Confused

anyway here's my explanation, not sure whether correct anot

When u mix H2SO4 (aq) with Mg(NO3)2 (aq), the acid does not dissociate its ions (H+ and SO4 2-), therefore they wont "look for and combine with" the Mg2+ and NO3- ions

hope it's correct Laughing cos i anyhow crap 1

absol SG

qns 1

C.
magnesium nitrate is a salt. so if u add sulphuric acid in, its a case of displacement. the hydrogen ion is less reactive than magnesium ion, so theres no way of magnesium being displaced by hydrogen and so there's no reaction.

the other options can react with sulphuric acid because
-magnesium hydroxide(alkali) and magnesium oxide(basic oxide) reacts with sulphuric acid to result in a neutralisation action, ie salt and water are produced.

-magnesium metal will react with sulphuric acid..to form...magnesium sulphate and hydrogen gas if im not wrong o.0 Rolling Eyes

^tamago^ SG

Sometimes try to answer 'O' level questions in 'A' level way can cause you to lose marks. Laughing

Darkness_hacker99 SG

x2!

davidche SG

i tot nitrates are soluble?

wishboy SG

dunno leh
i tot (aq) means soluble in water nia

^tamago^ SG

Actually since the nitrates is a MCQ, you are not required to know why this happens for 'O' Levels. Just take it that the rest will react and eliminate them to get Magnesium Nitrate.

Nitrates don't react with H2SO4 but with chloride/iodide/bromide salts.

Reactivity Series for Anions:
I (most reactive)
Br
OH
Cl
NO3
CO3
SO4 (least reactive)

OasisBlue SG

well my teacher said it's nitrate too

davidche SG

soluble + soluble = what?

tanjun SG

Let me try explaining the first qn.

Magnesium nitrate is a soluble salt while magnesium sulphate should be a soluble salt. I am not sure the reason but I guess it has got to do with the balance of ion dipole attraction and id-id attraction.
What I have been taught during my secondary school days are only 3 sulphates are insoluble in water and they are calcium sulphate, lead (II) sulphate and barium sulphate.

Anyway, when sulphuric acid containing hydrogen ions and sulphate ions is added into a solution containing magnesium ions, nitrate ions, hydrogen ions and hydroxide ions, it is merely an addition of ions into the solution. Reason: as stated above.

If barium nitrate is used instead of magnesium nitrate. A visible reaction will occur.
BaSO4 (s) reversible sign Ba2+ + S042-

As concentration of SO4 2- increases, equilibrium will tend to the left for reversible reactions to counteract the change. Therefore, BaS04 (s) will form.