# Chemistry help!!

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#1
Can anyone help me with these??
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#2
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3 years ago
#3
(Original post by Lucky10)
Can anyone help me with these??
?
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3 years ago
#4
m= mass of solution, equal to total volume (e.g in first one its 50)
c= specific heat capacity, 4.18 for water
delta T= change in temp- t2-t1

delta h, enthalpy of solution-= Q/n where n is number of moles, found in normal mass/mr way
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#5
(Original post by Hajra Momoniat)
?
Ive posted it now
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3 years ago
#6
which q?
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#7
m= mass of solution, equal to total volume (e.g in first one its 50)
c= specific heat capacity, 4.18 for water
delta T= change in temp- t2-t1

delta h, enthalpy of solution-= Q/n where n is number of moles, found in normal mass/mr way
Could you show me an example with the first one please
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3 years ago
#8
q=mc delta t
m=25+25= 50g as 1g is approx 1 cm cubed
c=4.18
delta t= 12
q=50*4.18*12=2508J

can you find the moles and use that to find delta h? using delta h= q/n
you can also use the equation n= conc* vol to find moles
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#9
The question itself
(Original post by 06moca1)
which q?
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#10
q=mc delta t
m=25+25= 50g as 1g is approx 1 cm cubed
c=4.18
delta t= 12
q=50*4.18*12=2508J

can you find the moles and use that to find delta h? using delta h= q/n
you can also use the equation n= conc* vol to find moles
I'm not sure
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3 years ago
#11
(Original post by Lucky10)
I'm not sure
n=2.00*25/1000=0.05
can you finish?
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#12
n=2.00*25/1000=0.05
can you finish?
is the change -1.254?
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3 years ago
#13
(Original post by Lucky10)
is the change -1.254?
Not quite, we have q= 2508 and n=0.05 and delta h=q/n
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#14
Not quite, we have q= 2508 and n=0.05 and delta h=q/n
Don't we need to divide it by 1000? Also isnt change in minus?
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3 years ago
#15
(Original post by Lucky10)
Don't we need to divide it by 1000? Also isnt change in minus?
Divide the Delta h by 1000- you can but its easier to do at end of calculation- delta h=-q/n but its easier to use q/ n and convert at the end depending on whether the reaction is exothermic or endothermic- this one is exo so it is negative so answer is 2508/0.05=50160j/mol, you can divide by 1000 to get 50.16kj/mol and put a negative as its exo for final answer of -50.16kj/mol
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#16
Divide the Delta h by 1000- you can but its easier to do at end of calculation- delta h=-q/n but its easier to use q/ n and convert at the end depending on whether the reaction is exothermic or endothermic- this one is exo so it is negative so answer is 2508/0.05=50160j/mol, you can divide by 1000 to get 50.16kj/mol and put a negative as its exo for final answer of -50.16kj/mol
I thought like you divide the 2508j by 1000? Or is it already converted? So how do you if it's exo or endo and so question will be 100x4.18x18.8??
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3 years ago
#17
(Original post by Lucky10)
I thought like you divide the 2508j by 1000? Or is it already converted? So how do you if it's exo or endo and so question will be 100x4.18x18.8??
you can divide it by 1000- do that if youre comfortable- i suggested doing that at the end but whatever youre used to and im looking at q1 where the temp change is 12 and mass=50, exo and endo is deduced from whether temp has risen or fallen- if surroundings risen, exothermic - if surrounding temp fallen, endothermic
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#18
you can divide it by 1000- do that if youre comfortable- i suggested doing that at the end but whatever youre used to and im looking at q1 where the temp change is 12 and mass=50, exo and endo is deduced from whether temp has risen or fallen- if surroundings risen, exothermic - if surrounding temp fallen, endothermic
So would q2 be 100x4.18 x 18.8?
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3 years ago
#19
(Original post by Lucky10)
So would q2 be 100x4.18 x 18.8?
no, total mass = 100+100=200
Delta t= 6.8
q= 200*4.18*6.8
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#20
no, total mass = 100+100=200
Delta t= 6.8
q= 200*4.18*6.8
Alright I got you can you help me on 4c that's it
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