Year 12s: what will be the first way you research your future options? >>

Help with 2 chemistry questions please :(

Need help with these as I have no idea at all

Q1) what mass of solid Zinc nitrate --Zn(No3)2-- is required to make 250mL of a 0.1mol/L aqueous solution.

Q2) What volume of water must be added to 50mL of 1mol/L hydrochloric acid to produce a solution with a concentration of 0.050 mol/L?

Reply 1

jeoja

Hi. I'll start by giving some formulae/concepts you need to solve the questions to see if you can work it out from there. If not then I'll give further help :smile:

Q1) 250ml = 0.25l (I know this is a bit obvious but could be easy to forget to convert)
mol = concentration * volume
mass = mol * Mr

From the above information you can figure out how many moles you need of the zinc nitrate to get that concentration for the stated volume, and therefore the mass.

Q2) 50ml = 0.05l
mol = concentration * volume

For this one I could be wrong but I think it ends up being simpler than it sounds. Once you find the moles of HCl you have in 0.05L you only need to do a quick subtraction to find the answer if you think about what all of the units mean. I appreciate this help is a bit vague but if you can figure it out for yourself I don't want to give too much away and take away any satisfaction!