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Been at this question for ages? HELP!?!?

Zinc chloride can be prepared in the laboratory by the reaction between zinc oxide and
hydrochloric acid.
The equation for the reaction is
ZnO + 2HCl ZnCl2 + H2O
A 0.0830 mol sample of pure zinc oxide was added to 100cm3 of 1.20 moldm–3
hydrochloric acid.
Calculate the maximum mass of anhydrous zinc chloride that could be obtained from
the products of this reaction.

I managed to get an answer of 8.184g of ZnCl2 ---- 0.1dm-3 x 1.2 moldm-3 = 0.12mol

0.12/2 (1:2 ratio) = 0.06
Mr ZnCl2 = 136.4
0.06 x 136.4 = 8.184g?

Am I doing this right because by doing my method I completely ignore the moles value for the pure zinc oxide (0.0830mol). Any help would be greatly appreciated thanks :smile:

(edited 10 years ago)

Reply 1

Solivagant

Yes, you are doing it right :smile:

You have less HCl than ZnO in terms of moles, so the HCl is the limiting agent, and not all of the ZnO can be converted.

Reply 2

dasda

thanks

Original post by Solivagant

Yes, you are doing it right :smile:

You have less HCl than ZnO in terms of moles, so the HCl is the limiting agent, and not all of the ZnO can be converted.

Reply 3

evelynpark

i don't understand though because in order for HCl to have less moles you divide by 2 sorry I'm having a brain fart rn i can't get my head round this someone pls explain

Reply 4

dasda

HCI has two moles. Zncl2 has 1 mole. Therefore you calculate the moles of HCI by using the concentration equation and then divide by 2 since that's the ratio. The topic is called stoichiometry(I don't know if I spelled it right)

Original post by evelynpark

i don't understand though because in order for HCl to have less moles you divide by 2 sorry I'm having a brain fart rn i can't get my head round this someone pls explain