Titration calculation

Idenify the R.A.M. of a metal X form the following data: 1.0g of the anhydrous carbonate X2CO3 was added to 50cm3 of hydrochloric acid of concentration 1.0moldm3. The remaining acid after reaction was complete required 30.0cm3 of 1.0moldm3 sodium hydroxide for neutralisation.

Hello,

Firstly, you should begin by calculating the volume of HCl required in the neutralisation reaction; if you know the volume and concentration of the NaOH, you can calculate the number of moles which react (the number of moles of HCl is the same if you look at the reaction equation). You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.

Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl, which is then used to calculate the number of moles of the X carbonate (once again using a chemical equation). Once this is known, the molar mass of the substance can be calculated. You can then take off the molar mass of the carbonate part of the formula to find the molar mass of the X_2. It is then a simple case of diving by 2 to obtain the RAM of X.

If anything has been unclear, please ask. I may even be kind enough to check your answer as well. ;-)

"You can now take the number of moles and multiply it by the concentration of 1.0M to get the volume in cubic decimetres.Secondly, you should take this value away from the original volume of HCl to find the reacting volume in the initial reaction. You can then use this to calculate the reacting moles of HCl"

Thanks for the help! Much appreciated. However, I'm still unsure on this bit. Surely to find the moles you divide it by the concentration??(it doesnt really matter anyway because the value is 1)

Also, how can you use the new value to work out the reacting volume when I thought we already have that value: 50cm3

When i tried the calculation, I came to an Mr of 0.002 so i assume I've done it completely wrong

Hello again,

Sorry to keep you waiting. As for your first query, as concentration C = n/V,
n = CV

As for your second query, I think that you've fallen for the question's little trap. The 50cm³ of HCl was in excess, thus meaning some was left over. You therefore need to calculate how much was in the second reaction and then take that off the total acid volume to find the volume which reacted with 1.0g of the carbonate.

Your final answer is rather strange as I'm sure you've noticed. I may write a full working for you, but I may be some time.

Good luck :-).

PS: sorry if my first reply was confusing- it had been a long day.

Hmmm. This doesnt seem to be coming easy to me. Still a bit stuck despite your excellent help. This is what I've managed to do so far:

Moles of NaOH = 0.03*1 = 0.03moles
(2nd reaction) Moles of HCl = 0.03
(1st reaction) Moles of HCl = 0.05*1 = 0.05 moles

0.05-0.03=0.02moles

moles of X2CO3 = 0.02/2 = 0.01

That's where I'm to and now have no clue what to do!

If possible, and I understand you have a life, could you push me in the right direction please. I find these so tricky

Thanks for all your help!