hey everyone, can someone please help me with this? when do you comment about electrons filling orbitals and when electrons fill subshells? i don't quite know when to use with term :/
Electrons fill up orbitals. A subshell is a group of orbitals eg the 3p subshell contains 3 p orbitals each with up to 2 electrons in each orbital
Yeah I mean a B isn't too bad considering I literally thought I knew nothing about chemistry, but after revising I feel more confident apart from the bloody intermolecular bonding and stuff which is just so annoying. If I can get near full marks in the section B part of the paper which I really like it will bump up my grade
Btw you done the chem empa paper? I would really like the answers
Spoiler
Then you've done quite well considering that you haven't revised much then
I won't. I just find it really really irritating to get so many people asking for EMPA and ISAs answers and stuff. I get loads of PMs asking for them and it boils my blood... And anyway, I'm on Edexcel
Yeah that's what I meant, wow that's behind but its possible, you'll just need to put in a lot of work! You'll be fine
Lol its physically impossible to finish the book between now and then as I've got two other subjects. I'm doing terrible in my practicals too. This isnt going to end well.
Guys/girls, this question has been bothering me for a while now, would really like some help, would be much appreciated.
0.85g of an indigestion tablet containing calcium hydroxide was was reacted with 50cm3 of 1.00M hydrochloric acid. the resulting solution was made up to 250m3 in a volumetric flask. 25cm3 of this solution required 30.80cm3 of 0.100M sodium hydroxide for neutralisation. calculate the per cent purity, by mass of the calcium hydroxide.
So I calculated the moles of sodium Hydroxide, by using n= cv, so n = (0.100 x 30.80/1000) =0.00308 Moles
NaOH + HCL -> Nacl + H20, so they react 1:1, the moles of HCl must also equal 0.00308 moles.
but now what do I do?
The moles of HCl you have calculated is the I reacted HCl. Now answer those questions How many moles of HCl are there in 250cm3? How many moles of HCl were there initially? How many moles of HCl reacted with calcium hydroxide? What is the ratio of reaction between HCl and calcium hydroxide? What is the molar mass of calcium hydroxide? What is the mass of calcium hydroxide in the tablet? What is the percentage purity by mass?
The moles of HCl you have calculated is the I reacted HCl. Now answer those questions How many moles of HCl are there in 250cm3? How many moles of HCl were there initially? How many moles of HCl reacted with calcium hydroxide? What is the ratio of reaction between HCl and calcium hydroxide? What is the molar mass of calcium hydroxide? What is the mass of calcium hydroxide in the tablet? What is the percentage purity by mass?
ok so in the 250cm3, n=cv, so 1.00m x 250/1000= 0.25moles initially, there was, 1.00M x 50/1000= 0.05moles
well 0.05 moles.
1:1
57
0.85,
erm....
Sorry I meant uncreated HCl in the first sentence
You multiply your calculated moles of HCl by ten because 25cm3 was used out of 250cm3. Volumetric flask business was AFTER HCl was reacted so you don't know the concentration of the HCl in volumetric flask
And ratio is 2HCl+Ca(OH)2 ---> CaCl2+2H2O so it's 2:1
Then you've done quite well considering that you haven't revised much then
I won't. I just find it really really irritating to get so many people asking for EMPA and ISAs answers and stuff. I get loads of PMs asking for them and it boils my blood... And anyway, I'm on Edexcel
Haha yeah thanks, tbh chem isn't that bad it's just certain topics that I find hard.
Same here I have like 11 unopened messages atm on top of probably 15 others I opened all about the bio empa :/
I find the topics aren't that bad, its the actual exam, sometimes they word questions really weirdly
And just saying believe it or not, Edexcel is harder than AQA. I'm on Edexcel by the way and AQA looks like fun compared to Edexcel
Yeah, they do and it sometimes is pretty confusing, but with more past papers, you see the trends and know what to put for the answer. Tbh that's a good thing for me because I get an easy exam spec (although I am gonna fail anyway )
I think someone called Adamkahn has, might wanna message him
Yeah, they do and it sometimes is pretty confusing, but with more past papers, you see the trends and know what to put for the answer. Tbh that's a good thing for me because I get an easy exam spec (although I am gonna fail anyway )
Yeah I guess Just make sure you do loads of past papers and understand where you're going, it helps