Great, maybe you can help me solve some 
Can you help me with this one please?
http://prntscr.com/jpjedo
Can you help me with this one please?
http://prntscr.com/jpjedo
Original post by Grizzelex
Great, maybe you can help me solve some
Can you help me with this one please?
http://prntscr.com/jpjedo
Can you help me with this one please?
http://prntscr.com/jpjedo
Calculate moles of O2, then double it for oxygen ions. Calculate moles of 1 gram of each metal. Then see what matches, remembering that if the metal is group 1, then there'll be two metal ions for each oxygen ion. The answer is calcium I believe.
Original post by Thizzumri
Calculate moles of O2, then double it for oxygen ions. Calculate moles of 1 gram of each metal. Then see what matches, remembering that if the metal is group 1, then there'll be two metal ions for each oxygen ion. The answer is calcium I believe.
Yes, that's it! But why double the moles?
Original post by Grizzelex
Yes, that's it! But why double the moles?
O2 + 4e– --> 2 O2–
Original post by Thizzumri
O2 + 4e– --> 2 O2–
Thank you.
Original post by makami11
This question is from an AQA exam, it seems really easy but I still can't find a solution for it. Can you get the answer???
I got C. Using the ideal gas equation, you can work out the number of moles of gas. You've got 0.170 dm3 of gas. Substitute and rearrange the equation to find moles. Then, substitute this value for moles into the ideal gas equation, this time using the volume value of 0.5, and you rearrange to find p (I calculated it with atm rather than kPa, meaning I had to divide by 100 initially, then multiply by 100 at the end)
Original post by Thizzumri
An easier way to find the answer if you spot it. Treat the initial volume as 0.17dm3. The final volume is 0.5. So 0.5/0.17 shows you by what factor the pressure decreases. 100÷(0.5/.17) gives you 34.
Ok hat off to you for 2 solutions! The first one seems so long for a 1 marker, think I had only 30 sec left to answer it. Thanks it does make a lot of sense now
Original post by makami11
Ok hat off to you for 2 solutions! The first one seems so long for a 1 marker, think I had only 30 sec left to answer it. Thanks it does make a lot of sense now
Yeah, with multiple choice questions, if you think your method will take too long, that's generally because there's a quicker way to do it.
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