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View Full Version : To Chemistry experts - I NEED YOUR HELP!!!!!!!

Chunchun
Dec 18th, 2004, 02:47 AM
If you know how to do my fucking homework, Help me plzzzz :bowdown:

Write a Chemical equation for 1 & 2:
1 Calcium carbonate solid and dilute nitric acid
2 Zinc carbonate and dilute sulphuric acid

3 5.80 g of a gaseous compound X (containing carbon and hydrogen only) were completely burnt in excess dry oxygen. The products were passed through a suitable drying apparatus containing anhydrous calcium chloride, and it was found that 9.00 g of water had benn formed.
(a) Calculate the mass of hydrogen in 9.00 g of water.
(b) Calculate the mass of carbon in 5.80 of X.
(c) Find the empirical formula of X.

Multiple Choice
4 13.70 g of an oxide of metal X (relative atomic mass = 207.0) reacts with excess hydrogen to produce 1.44 g of water. What is the empirical formula of the oxide?
A. XO
B. XO2
C. X2O
D. X3O4

5 A mixture of magnesium chloride and magnesium sulphate contains 0.6 mole of chloride ions and 0.2 mole of sulphate ions. The number of moles magnesium ions present is
A. 0.4 mol.
B. 0.5 mol.
C. 0.8 mol.
D. 1.0 mol.

moby
Dec 18th, 2004, 03:17 AM
have you tried it yourself? you should, cause stoichiometry apparently requires lots of practice
hint: write your stoichiometric equations first
3 is slightly more challenging than the rest, so what you could do is to write the equation of combustion first

CxHy + (y/4 +x) O2 --> y/2 H2O + xCO2

then solve for x and y, since you do know the amount of water produced

Cuckoo
Dec 18th, 2004, 03:18 AM
If you know how to do my fucking homework, Help me plzzzz :bowdown:

Write a Chemical equation for 1 & 2:
1 Calcium carbonate solid and dilute nitric acid
2 Zinc carbonate and dilute sulphuric acid

CaCO3 + 2HNO3 = Ca(NO3)2 + H20 + C02

ZnCO3 + H2SO4 = ZnSO4 + CO2 + H20

Their both carbonate reactions carbonate + acid = Metal + C02 + Water etc

I can do the other ones but dont have time, so good luck.

Chunchun
Dec 18th, 2004, 07:48 AM
thx folks :wavey:

infact i know carbonate + acid = Metal + C02 + H2O,
i just dun no how to balance the equation :p

Cuckoo
Dec 18th, 2004, 08:04 AM
oh thats simple, i can teach u if u want.

Ting
Dec 18th, 2004, 09:22 AM
I can't be bothered to do all the calculations:p You can work out the balanced equation from oxidation numbers, that's how I find easier to do:)