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chemistry

hello there can anyone help me with this following question please
A student was asked to carry out an experiment to determine the initial rate of reaction of zinc and hydrochloric acid.
The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of zinc.
The student selects the following apparatus:
the apparatus shown in the diagram
100 cm3measuring cylinder
stop clock
2 decimal place balance
Outline how the student could carry out the experiment and explain how the results could be processed graphically.
Show all working in your calculations.
https://pmt.physicsandmathstutor.com/download/Chemistry/A-level/Topic-Qs/OCR-A/3-Periodic-Table-and-Energy/Set-G/3.2.2%20Reaction%20Rates%20QP.pdf

question 5 I got everything but the calculations part I don't know how to get to the concentration of HCl
(edited 9 months ago)
Original post by cr7090121
hello there can anyone help me with this following question please
A student was asked to carry out an experiment to determine the initial rate of reaction of zinc and hydrochloric acid.
The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of zinc.
The student selects the following apparatus:
the apparatus shown in the diagram
100 cm3measuring cylinder
stop clock
2 decimal place balance
Outline how the student could carry out the experiment and explain how the results could be processed graphically.
Show all working in your calculations.
https://pmt.physicsandmathstutor.com/download/Chemistry/A-level/Topic-Qs/OCR-A/3-Periodic-Table-and-Energy/Set-G/3.2.2%20Reaction%20Rates%20QP.pdf

question 5 I got everything but the calculations part I don't know how to get to the concentration of HCl

Well, start by doing the two following things:

(A) write an equation for the reaction between Zn and HCl

(B) work out how many moles of HCl you will therefore need to react with the zinc to produce 72 cm^3 of H2 (this itself is not necessarily an easy task and should perhaps be broken up into stages)
Reply 2
Original post by TypicalNerd
Well, start by doing the two following things:

(A) write an equation for the reaction between Zn and HCl

(B) work out how many moles of HCl you will therefore need to react with the zinc to produce 72 cm^3 of H2 (this itself is not necessarily an easy task and should perhaps be broken up into stages)

I did all of that and somehow I just cant get it right
for b your going to need to have 6x10-3 as its a 1:2 ratio for zinc and HCl accordingly we also know that its at rtp and standard conditions so I thought to myself I could perhaps use the pv=nrt as a last resort if I don't get it and I did go ahead and did it but the volume I got was completely wrong
Original post by cr7090121
I did all of that and somehow I just cant get it right
for b your going to need to have 6x10-3 as its a 1:2 ratio for zinc and HCl accordingly we also know that its at rtp and standard conditions so I thought to myself I could perhaps use the pv=nrt as a last resort if I don't get it and I did go ahead and did it but the volume I got was completely wrong

Do you know the volume occupied by 1 mole of gas at RTP (you should be aware of this if you are doing OCR A/B or Edexcel)?
Reply 4
Original post by TypicalNerd
Do you know the volume occupied by 1 mole of gas at RTP (you should be aware of this if you are doing OCR A/B or Edexcel)?


I do know that and its quite irrelevant as we are dealing with a liquid HCl is a liquid
Original post by cr7090121
I do know that and its quite irrelevant as we are dealing with a liquid HCl is a liquid

No it’s not irrelevant. The question says the following:

“The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of zinc.”
(edited 9 months ago)
Reply 6
Original post by TypicalNerd
No it’s not irrelevant. The question says the following:

“The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of zinc.”


how is that going to help other than giving me the moles of zinc and hydrogen and Hcl which I already have , the main question is too find the volume of Hcl
(edited 9 months ago)
Original post by cr7090121
how is that going to help other than giving me the moles of zinc and hydrogen and Hcl which I already have


I had misread your previous post and was starting from the beginning as it wasn’t initially clear how far you had actually got as you hadn’t shown all your working.

But now you have the moles of HCl and you can reasonably infer what volume of HCl you’ll need from the capacity of the measuring cylinder, so how might that be useful?
(edited 9 months ago)
Reply 8
Original post by TypicalNerd
I had misread your previous post and was starting from the beginning as it wasn’t initially clear how far you had actually got as you hadn’t shown all your working.

But now you have the moles of HCl and you can reasonably infer what volume of HCl you’ll need from the capacity of the measuring cylinder, so how might that be useful?


so sorry I forgot to include my working out apologies. the capacity of the measuring cylinder is 100 cm3 how can I predict anything if I only got the moles and the reactants one is a solid and the other is a liquid and you cant really suppose that they are going to fill up the cylinder at a maximum capacity that's unrealistic
Original post by cr7090121
so sorry I forgot to include my working out apologies. the capacity of the measuring cylinder is 100 cm3 how can I predict anything if I only got the moles and the reactants one is a solid and the other is a liquid and you cant really suppose that they are going to fill up the cylinder at a maximum capacity that's unrealistic

No, it’s not unrealistic.

If you look up a picture of a 100 ml measuring cylinder, the 100 ml mark is well below the rim - you can fill it a little further than 100 ml, but 100 ml is as far as you can measure to a reasonable degree of accuracy.
Reply 10
Original post by TypicalNerd
No, it’s not unrealistic.

If you look up a picture of a 100 ml measuring cylinder, the 100 ml mark is well below the rim - you can fill it a little further than 100 ml, but 100 ml is as far as you can measure to a reasonable degree of accuracy.

still cant find answer it doesn't really help as zinc is a solid and you cant really find volume of it also you cant even find the volume of hcl either

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