[jennielynn_1980]

I did this question ages ago and now I am reviewing it and I don't know how I got my answer. 

The question is:
A compound containing titanium and chlorine is analyzed by converting all the titanium into 1.20g of TiO₂ and all the chlorine into 6.45 of AgCl.  What is the simplest formula for the original compound.

So this is what I did:

Molar mass of TiO2 = 79.88g/mol
Moles of Titanium = 1.20 = 0.0150 moles of TiO₂
                                79.88

For every mole of TiO₂ compound there is 1 mole of Titanium atoms (HOW DO I KNOW THAT? WHY IS IT THE RATIO NOT 1:2 INSTEAD OF 1:1?)
Therefore there are 0.0150 moles of Titanium.

6.45g of AgCl the molar mass of this compound would be = 107.9 + 35.5 = 143.4 g/mol
Moles of chlorine = 6.45 = 0.0450 moles of chlorine
                              143.4

Ti:Cl
0.0150 : 0.0450
3:9
1:3

Therefore the simplest formula for the original compound is TiCl₃

I am pretty sure the answer is right.  I am just getting confused about the moles and ratios.

[Dan]

For every mole of TiO₂ compound there is 1 mole of Titanium atoms (HOW DO I KNOW THAT? WHY IS IT THE RATIO NOT 1:2 INSTEAD OF 1:1?)
Therefore there are 0.0150 moles of Titanium.

How many Ti atoms are there in one molecule of TiO₂?
So how many moles of Ti atoms are in 1 mole of TiO₂ molecules?

[jennielynn_1980]

Ti atoms in one molecule of of TiO₂ = 1.508 x 10²²

Moles of Ti atoms in 1 mole of TiO²
= 1.508 x 10²²                                                                
     6.02 x 10²³
=0.0250 x 10 ²³

So my answer was wrong?

Then it would be
Ti:Cl
0.0250:0.0450
5:9

Ti₅Cl₉?

[Borek]

Ti atoms in one molecule of of TiO₂ = 1.508 x 10²²

Take a look at the formula - it tells you how many atoms of Ti and O there are in the molecule.

One H₂O molecule contains 2 atoms of hydrogen and one atom of oxygen.

Note that mole is just a measure of quantity - like dozen. There are 12 items in dozen and 6.02*10²³ items in mole.

If there is one atom of O in water molecule, and there are 6.02*10²³ molecules in mole, how many atoms of O are in one mole of water?

[Donaldson Tan]

let T be mole of titanium present in 1.20g of TiO₂
let C be mole of chlorine present in 6.45g of AgCl

The product contain T moles of titanium and C moles of chlorine.

The ratio of T to C gives you the emperical formula of the product

[jennielynn_1980]

I think the ratio of Ti to O₂ is 1:1  because if you have say
Ca + 2H₂O --> Ca(OH)₂ + H₂
The ratio of Ca to 2H₂ is 1:2 because there are 2H₂ so if you have Ti and O₂ the ratio is still 1:1.  That would mean my first answer is correct (I hope)

[Borek]

I think the ratio of Ti to O₂ is 1:1  because if you have say
Ca + 2H₂O --> Ca(OH)₂ + H₂
The ratio of Ca to 2H₂ is 1:2 because there are 2H₂ so if you have Ti and O₂ the ratio is still 1:1

Depends on whether you refer to atoms or molecules.

[JZ_1]

For every mole of TiO₂ compound there is 1 mole of Titanium atoms (HOW DO I KNOW THAT? WHY IS IT THE RATIO NOT 1:2 INSTEAD OF 1:1?)

How many Ti atoms are there in one molecule of TiO₂?
So how many moles of Ti atoms are in 1 mole of TiO2 molecules?

He said molecules.. not moles. You don't need to calculate anything... just count it (look for the subscript). Therefore, there is ONE Ti atom in a molecule of TiO₂.

It is a 1:2 ratio IF AND ONLY IF you are calculating for OXYGEN atoms because there are TWO Oxygen atoms in a molecule of TiO₂.

Since in its sumplest form (molecule) the ratio of Ti in a molecule of TiO₂ is 1:1, it still holds true in a mole of TiO₂.

[Donaldson Tan]

I think the ratio of Ti to O2 is 1:1

But we are comparing the proportions of titanium to oxygen, not to di-oxygen. Can you see that we are doing an element-to-element comparision?

The molar ratio of Ti in TiO₂ to TiO₂ is 1:1, but the molar ratio of O in TiO₂ to TiO₂ is 2:1. Can you see why?

[skyglow1]

(HOW DO I KNOW THAT? WHY IS IT THE RATIO NOT 1:2 INSTEAD OF 1:1?)

Since TiO₂ is ionic, we are not really dealing with "1 molecule" of TiO₂ and its molar mass in our calculations, but rather 1 formula unit of TiO₂.

So, in 1 formula unit of TiO₂, we can see there is 1 atom of Ti.

Since moles is simply a measure of amount, if there is 1 mole (6.02x10^²³) of TiO₂ formula units, there will be 1 mole of Ti atoms too. Thats why the ratio is 1:1.

[jennielynn_1980]

It dawned on me today.  I get in it now.  I was overthinking the whole thing in terms of numbers and moles and molecules and atoms when the answer is so much simpler than that.  Thank you all for explaining it to me.