Post by: psychlaw on July 19, 2008, 12:36:01 am
For Now
(1) Balance this equation, I don't know how to do subscript numbers so I'll try and write/explain it as best as I can
NaOH + Cl2 --> NaCl + NaClO3 + H20 (this is water, not H and two oxygens)
Also
(2) Iron Pyrites has the forumula FeS2 (2 is a subscript :D). When this solid is roasted in air, it reacts to form iron (III) oxide and sulphur dioxide gas.
What mass of iron (III) oxide is obtained by the roasting of 5000kg of iron pyrites which is 60% pure?
Thanks all
Post by: Toothpaste on July 19, 2008, 12:40:27 am
Post by: psychlaw on July 19, 2008, 12:42:12 am
Post by: Collin Li on July 19, 2008, 12:49:20 am
This is because the elements balance (same number of Fe).
So, if I have 5000kg of iron pyrites of 60% purity, then I really only have:
Now, convert to moles, then multiply by half (because that's how much iron (III) oxide you'll make), and then multiply by the molar mass to get back to mass)
Note that the fraction on the right is the molar mass of iron (III) oxide divided by the molar mass of iron pyrite. This effectively converts the mass of iron pyrites into the mass of iron (III) oxide (divide by molar mass of iron pyrite to get moles, then multiply by molar mass of iron (III) oxide to get mass).
Post by: Collin Li on July 19, 2008, 12:57:49 am
NaOH + Cl2 --> NaCl + NaClO3 + H20 (this is water, not H and two oxygens)
One thing I always find weird is that I see "H20" commonly written, as opposed to "H2O". Why do people think the oxygen is a "0" (zero)?
Anyway, I made this post to point out that anyone who can read chemical notation should understand that the 2 belongs to the H.
The only time when the preceding number tells you about following item is when there is a big number before an entire species in a reaction. For example: H2SO4 + 2NaOH --> NaSO4 + 2H2O
In H2O, the 2 is in the middle of a species, so it definitely means the 2 is going to be a subscript, and hence, the 2 belongs to the element it is a subscript to (Hydrogen).
I don't know if you already knew this, but I'm just pointing it out.
Post by: lanvins on July 19, 2008, 02:44:13 pm
Post by: orangez on July 19, 2008, 07:11:10 pm
Post by: Mao on July 19, 2008, 07:59:39 pm
| solution | solute(M) | H3O+ | OH- | |
| HCl | 0.01 | 0.01 | 10-12 | acidic |
| HNO3 | 0.03 | 0.03 | 3.33*10-13 | acidic |
| NaOH | 0.02 | 5*10-13 | 0.02 | basic |
| Ca(OH)2 | 0.001 | 5*10-12 | 0.002 | basic |
Post by: psychlaw on July 20, 2008, 01:08:38 am
In the blast furnace, iron (III) oxide reacts with carbon monoxide to form iron and carbon dioxide. Carbon monoxide is a gas which forms in the blast furnace as a result of reaction between carbon and oxygen at a high temperature.
(1) What mass of iron may be obtained from 2250 kg of iron (III) oxide?
(2) What mass of carbon must be present to produce 1000 tonne of iron?
Post by: Collin Li on July 20, 2008, 01:18:46 am
To produce 1000 tonne of iron by carbon, first we need to balance the equation to find out the stoichiometric ratio:
Balanced equation:
And, carbon monoxide is formed by:
Now, let's do this in a methodical way (the above solutions I've offered have been an 'express' method because they were pretty simple questions):
Post by: psychlaw on July 20, 2008, 01:20:55 am
Also with your last post, answering my question about the iron pyrites, what is the "159/120" for?
Isn't it supposed to be 3000/120 for the mol calculation. The 3000 is the mass and the 120 the molar mass?
Post by: Collin Li on July 20, 2008, 01:22:43 am
Normally, you'd divide by 120 first, write down the number of moles, then multiply by 1/2, write down the number of moles of that, then multiply by the molar mass, to get the mass, which takes 3 lines! I took 1.
Post by: psychlaw on July 24, 2008, 08:19:48 pm
This is the easiest of 10 questions I have to do (but at the moment I have no clue how to do them) so if somebody could please just do this question for me, so then I can work out the rest using this as the example:D
thanks guys!!!
Post by: Mao on July 24, 2008, 08:35:22 pm
since the number of moles of water is more than double that of calcium carbide, calcium carbide is our limiting reactant:
stoichiometry: the mole ratio of ethyne to calcium carbide (from the equation) is 1:1, hence
Post by: psychlaw on July 24, 2008, 10:30:05 pm
n (c2h2) = n(CaC2) = 1.248 mol????
I think im lost because there arent any numbers or answers =/
Post by: psychlaw on July 24, 2008, 10:37:38 pm
Post by: Mao on July 25, 2008, 04:43:32 pm
what exactly do u mean by
n (c2h2) = n(CaC2) = 1.248 mol????
I think im lost because there arent any numbers or answers =/
previous post updated
Post by: psychlaw on July 28, 2008, 07:32:40 pm
(calcium oxide is slightly soluble)
since the number of moles of water is more than double that of calcium carbide, calcium carbide is our limiting reactant:
stoichiometry: the mole ratio of ethyne to calcium carbide (from the equation) is 1:1, hence
Wrong :) Answer is 32.5 But your steps are right, just misadded the Molar mass of C2H2. I get it now anyway :D except this new question (still easy)
Calcium Oxide and Carbon react to produce calcium carbide, CaC2, and carbon monoxide. What is the maximum mass(that part confuses me) of calcium carbide that can be obtained from 40 kg of calcium oxide and 40 kg of carbon?
Post by: Mao on July 28, 2008, 08:08:44 pm
n(CaO)=40000/(40.1+16)=713 mol
n(C)=40000/12=3333 mol (more than 3 times that of CaO, hence CaO is the limiting reactant)
n(CaC2) = 713 * (40.1+12*2) = 45.7kg
maximum mass in this case, I think, refer to the theoretical yield, i.e. the reaction proceeds to completion rather than equilibrium. [you don't need to know that yet]
for the purposes of unit 2 [and 3 for that matter], all of the reactants react to form as much product as possible [except for the species in excess]
Post by: psychlaw on July 30, 2008, 05:50:46 pm
In the blast furnace, iron and carbon dioxide are formed from the reaction between iron (III) oxide and carbon monoxide, which itself is formed from the reaction between Coke (C) and oxygen. What is the maximum mass of iron that can be obtained from 700 tonnes of iron (III) oxide and 70 tonnes of coke?
Post by: Mao on July 31, 2008, 08:39:04 pm
and
(i think...)