Chemistry alevels pag 1.2 extension

Hi there,

I was wondering if anyone could help me with this extension question for pag 1.2 to work out the percentage uncertainty I have the equation however I am not sure which values to use. If someone could help that would be great.
Thanks 🙏

You have your tolerance value, e.g the mass balance is accurate to 2 d.p, so if it said 5.00g it could be less than 5.004g or greater than 4.995g
So the tolerance value would be 0.005
If you used the mass balance once, than it would be:
(0.005 x 1)/mass recorded x 100 to be a %

So I would have to use 0.005 and multiply to 1 and divide the mass of mg which was 0.060g and multiple to 100 is that it ?
So it would be 8.33% ??

I just used that one as an example.
I cant seem the find your question online so
% uncertainty = (number of readings used x error value)/actual value x 100
error value is the tolerance
number of readings = number of times you used it to measure the magnesium

There is also % error in recording the hydrogen gas produced
Everything you have recorded yourself, mass of __, volume of gas, will have % error

What’ numbers do I have to use for the actual value number of reading which was only one and errror value because I am still confused ?