# Chemistry a level

Another one😭😭

14.4 g of an element X react with oxygen to form24.0 g of a compound XO
Which element is X?

A) Fluorine

B )Magnesium

C )Titanium

D ) Molybdenum

I knew it wasn’t mg bc thats a group 2 metal but like how would i get titanium
Original post by Arii256
Another one😭😭

14.4 g of an element X react with oxygen to form24.0 g of a compound XO
Which element is X?

A) Fluorine

B )Magnesium

C )Titanium

D ) Molybdenum

I knew it wasn’t mg bc thats a group 2 metal but like how would i get titanium

They tell you that there were 14.4 g of the metal and this reacted with oxygen to form 24.0 g of the oxide.
From that, first work out how much oxygen was added to the metal and work out how many moles of oxygen atoms that is equivalent to.
Original post by TypicalNerd

They tell you that there were 14.4 g of the metal and this reacted with oxygen to form 24.0 g of the oxide.
From that, first work out how much oxygen was added to the metal and work out how many moles of oxygen atoms that is equivalent to.

So would the mass of oxygen added be 24.0-14.4? And then the moles just 9.6/32?
Original post by Arii256
So would the mass of oxygen added be 24.0-14.4? And then the moles just 9.6/32?

That would be how you correctly find the moles of O2 molecules that the metal reacted with.

It may actually be easier to find just find the moles of oxygen atoms in this case, so you would instead divide the 9.6 g by 16.
Original post by TypicalNerd

That would be how you correctly find the moles of O2 molecules that the metal reacted with.

It may actually be easier to find just find the moles of oxygen atoms in this case, so you would instead divide the 9.6 g by 16.

Sorry, you know for this i did 9.6/16 and got 0.6, do i multiply this by 14.4? And assume the mole ratio is 1:1?
Original post by Arii256
Sorry, you know for this i did 9.6/16 and got 0.6, do i multiply this by 14.4? And assume the mole ratio is 1:1?

Okay, there are 0.6 mol of oxygen atoms and you are correct that the ratio of M to O is 1:1, so there must also be 0.6 mol of M in the 14.4 g.

What does that make the relative atomic mass of M?
Original post by TypicalNerd

Okay, there are 0.6 mol of oxygen atoms and you are correct that the ratio of M to O is 1:1, so there must also be 0.6 mol of M in the 14.4 g.

What does that make the relative atomic mass of M?

0.6 x by 14.4 which is 8.64? And thats not the mr of titanium
Original post by Arii256
0.6 x by 14.4 which is 8.64? And thats not the mr of titanium

mol = mass/Mr

so

Mr = mass/mol
Original post by Arii256
0.6 x by 14.4 which is 8.64? And thats not the mr of titanium

No. You may find the equation (relative mass) x moles = mass useful.

However, even this does not give the Mr of titanium, which leads me to believe the formula of the oxide should have been MO2 and not MO.
(edited 6 months ago)
Original post by charco

mol = mass/Mr

so

Mr = mass/mol

Thats such a stupid mistake thanks
Original post by TypicalNerd

No. You may find the equation (relative mass) x moles = mass useful.

However, even this does not give the Mr of titanium, which leads me to believe the formula of the oxide should have been MO2 and not MO.

Might be a typo, i got the question at the end of this enthalpy booklet my teacher gave us
Original post by Arii256
Might be a typo, i got the question at the end of this enthalpy booklet my teacher gave us

No, it's not a typo.
"14.4 g of an element X react with oxygen to form 24.0 g of a compound XO. Which element is X?"
You correctly determined that there are 0.6 mol of oxygen.
You know that the mol of metal = mol oxygen
Therefore mass of metal/mol metal gives relative mass.