Amount of Substance question
1.00 g of sulphur dissolved completely in an excess of liquid ammonia to give 420 cm3 of hydrogen sulphide
(H2S), measured at 273 K and 101 kPa, and also a solid containing the elements nitrogen and sulphur. Deduce
the empirical formula of the solid.
The markscheme finds the number of moles of sulphur
1/32=0.03125 and then the number of moles of hydrogen sulphide= 0.42/22.4=0.01875
Could someone please explain why they divided it by 22.4??
(H2S), measured at 273 K and 101 kPa, and also a solid containing the elements nitrogen and sulphur. Deduce
the empirical formula of the solid.
The markscheme finds the number of moles of sulphur
1/32=0.03125 and then the number of moles of hydrogen sulphide= 0.42/22.4=0.01875
Could someone please explain why they divided it by 22.4??
This is based on OCR if you use another exam board they may still use 22.4
You would just skip the Pv = nRT and find moles by doing Volume (dm^3) / 24 (Or your molar gas volume)
Original post by Currygirl63
This is based on OCR if you use another exam board they may still use 22.4
This is based on OCR if you use another exam board they may still use 22.4
Thank you so much! I don't do OCR, I do AQA. I guess it's an old spec question because I remember reading about 24dm3 for one mole of gas.
Original post by Currygirl63
This is based on OCR if you use another exam board they may still use 22.4
This is based on OCR if you use another exam board they may still use 22.4
The markscheme says the formula is NS, I'm assuming what you calculated is the molecular formula?
Original post by Currygirl63
You would just skip the Pv = nRT and find moles by doing Volume (dm^3) / 24 (Or your molar gas volume)
Ah yes, sorry about that, didn't read that bit 
Original post by knksj112
The markscheme says the formula is NS, I'm assuming what you calculated is the molecular formula?
It's ok. Thank you for the help.
Original post by Currygirl63
Ah yes, sorry about that, didn't read that bit
Original post by Currygirl63
This is based on OCR if you use another exam board they may still use 22.4
This is based on OCR if you use another exam board they may still use 22.4
How come u r using kPa instead of Pa for pressure in the first calculation?
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