The Mole Questions?

Question

My younger sister has asked for help with some chemistry homework she has been set and unfortunately I know nothing useful about The Mole. I have balanced the equations for her but that's as far as I can go without becoming totally flustered. Could someone either give a detailed method in basic basic basic terms lol on how to work out the following ... or if you're feeling ultra nice, the answers with workings out :) I shall be forever in your debt if you do.
So here goes:

1: What mass of CO2 is produced by the complete combustion of 12g of C?

2: Calculate the mass of S that must be burned to produce 64g of SO2.

3: When CaCO3 is heated it produces CaO and CO2. What mass of CO2 can be produced by heating 10g of CaCO3?

4: Mg reacts with h2SO4 to produce MgSO4 and H2. What mass of H would be produced by reacting 12g of Mg with excess H2SO4?

5: Calculate mass of C needed to reduce 15.9g of copper(II) oxide:
CuO(S) + C(s) --> Cu(s) + CO(g)

Any help greatly appreciated.

Answer 1

Question one:
12g of carbon is 1 mole, so it will produce 1 mole of carbon dioxide, i.e. 44g .

Question two
64g of sulphur dioxide is one mole, so it will have been produced from 1 mole of sulphur, i.e. 32g .

Question 3
10g of calcium carbonate is 0·1 mole (10 ÷ 100), so it will produce 0·1 mole of carbon dioxide: 0·1 x 44 = 4·4g .

Question 4
12g of magnesium is 0·5 mole (12 ÷ 24), so it will produce 0·5 mole of hydrogen: 0·5 x 2 = 1g .

Question 5
15·9g of copper(II) oxide is 0·2 mole (15·9 ÷ 79·5), so it will require 0·2 mole of carbon: 0·2 x 12 = 6g .

Note: In all these questions, the stoichiometry was 1:1, which made them very easy. Things become a bit more complicated with other stoichiometries.

Allan Deeds.

Answer 2

First the mole equation is moles= mass/relative molecular mass (or relative atomic mass when talking about a single element).

1. First work out the equation- C + O2 = CO2
So 1 mole of C reacts with 1 mole O2 to produce 1 mole CO2
Next work out how many moles of carbon in 12 g
Carbon has a atomic mass of 12 so 12/12 = 1mole of carbon.
Therefore you produce 1 mole of CO2.
The molecular mass of CO2 is (12+ (2*16)) (1 carbon and two oxygens) = 44
So to work out the mass you reaarange the first equation to get
Mass = moles x RMM
Mass = 1 x 44
Mass = 44g of CO2

2. Can be worked out the same way just in reverse. Write out the equation and you find-
1 mole reacts with 1 mole to give 1 mole.
moles = 64/64(RMM of SO2)
moles = 1
So there would be 1 mole of S
Mass = 1 x 32 (RAM of S)
Mass = 32g

3. Again a 1:1:1 reaction
RMM of CaCO3= 100
So moles = 10/100 = 0.1moles
So there is are 0.1moles of CO2 produced
Mass = 0.1 x 44
Mass = 4.4g CO2

Your sister should be able to work the last two out for herself from following this. You'll need the periodic table to work out the atomic/molecular masses.
Good luck. If you get stuck again add an update and I'm sure we can help.

Answer 3

for this you will need a periodic table

The larger of the 2 numbers with each element is the relative atomic mass.

now the atomic mass is the number of grams per mole of that element

for C this is around 12 meaning that 12g of C is about 1 mole.

A mole is 6*10^23 atoms (just a big number)

So for the first question you just need to find the mass of 1 mole of CO2 (which= 12+16+16 =44g)

Answer 4

A mole is 6 x 10^23 molecules, it is also the amount at which the mass is equal to the molecular weight in grams. The number of moles = mass (g)/ M.Wt. Work out the number of moles of each of your starting points:

e.g 12 g of Carbon M.Wt = 12 so 12/12= 1 mole.

Then mutiply that by the stoichiometry of the reaction

e.g 1 mole of carbon makes 1 mole of Carbon dioxide.

The work out the mass of your end point:
mass (g) = moles x M.Wt

To find 6the molecular weight you just add up the atomic masses of each element in the compound.

e.g CO2 M.Wt. = C 12 + 2x O 16.

Answer 5

In the two cases you may get 2 moles of NH3. through fact in the two cases you have a million mole of N2, the style of moles of H2 is thoroughly beside the point for this calculation. What happens is that a million molecule of N2 types 2 molecules of NH3. as a result a million mole of N2 will style 2 moles of NH3. It doesnt count how plenty H2 you have through fact as quickly as you have used up the only mole of N2, you haven't any longer any further with which to make any further products. desire this makes some style of sense

Answer 6

A mole of a chemical weighs the same as the atomic weight in grams. So, a mole of carbon weighs 12 grams and a mole of Oxygen atoms would weigh 16 grams. A mole of oxygen molecules would weigh 32 g.

So the answers to the questions would be as follows.

1 C (12g) + 02 (32g) = CO2 (44g)

2 S02=64g
02=32g
Therefore weight of Sulphur = 64g-32g = 32g

3 1 mole CaCO3 = Ca (40g) + C (12g) + 03 (48g)
=100g.
10g of CaCo3= 0.1 Mole
1 Mole of C02=44 g therefore 4.4g of CO2 would be produced

4 1 Mole of Mg is about 24g. 12g of Mg is 0.5 Mole and as 2 moles of hydrogen are produced by 1 mole of magnesium a total of 1g of hydrogen would be produced

5 1 Mole CuO weighs 63.5g (Cu) + 16g (O) = 79.5
15.9/79.5=0.2 Moles of CuO
0.2 Moles of carbon weighs 12*0.2 g=2.4g