chem (1 Viewer)

[maths lover]

can anyone help with question 24 in this paper, my test it tomorrow and im not sure if i have the right answer.
http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2008IndependentYearly.pdf
thankyou

 

[Cupcake16XD]

can anyone help with question 24 in this paper, my test it tomorrow and im not sure if i have the right answer.
http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2008IndependentYearly.pdf
thankyou

Not doing HSC (but VCE)

We have just started doing these stuffs, so not sure if it's anywhere near being right but yeah,

First calculate heat evolved when 0.01 mole CaCl2 is dissolved in 100mL water = 0.083 KJ
this must be equal to m x s x t
where:
m = mass of water take it as 100g as its density is 1
s =sp.heat of water in KJ =4.18J/g
t is difference in temp. If final temp. is T then t =T-18
Calculate T
100 x 4.18 x (T-18) = 0.083 x 1000
Sorry if this is like an EPIC fail ><

 

[RANK 1]

can anyone help with question 24 in this paper, my test it tomorrow and im not sure if i have the right answer.
http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2008IndependentYearly.pdf
thankyou

0.01 x 83 = 0.83 kj

∆H = -mc∆T

m=100
c=4.18 x 10^3
∆H= 0.83

0.83=100(4.18)∆T

therefore ∆T= 0.83/(100 x 4.18 x 10^3)
= 1.986

therefore 18 + 1.986 = 19.986
= 20 degrees (2 s.f)

 

[Cupcake16XD]

Looks correct Cupcake16XD.

haha yay!! *feels proud* <3

 

[RANK 1]

Not doing HSC (but VCE)

We have just started doing these stuffs, so not sure if it's anywhere near being right but yeah,

First calculate heat evolved when 0.01 mole CaCl2 is dissolved in 100mL water = 0.083 KJ
this must be equal to m x s x t
where:
m = mass of water take it as 100g as its density is 1
s =sp.heat of water in KJ =4.18J/g
t is difference in temp. If final temp. is T then t =T-18
Calculate T
100 x 4.18 x (T-18) = 0.083 x 1000
Sorry if this is like an EPIC fail ><

you did half of the question,

 

[Cupcake16XD]

you did half of the question,

lolol I know and you are the best ><

But still, I'm quite proud cause I suck at chem D:

And we are just starting this thingy

 

[RANK 1]

wat are the chem modules for VCE?

 

[Cupcake16XD]

wat are the chem modules for VCE?

Unit 1: The big ideas of chemistry
-Periodic table
-Materials

Unit 2: Environmental chemistry
-Water
-The atmosphere

Unit 3: Chemical pathways
-Chemical analysis
-Organic chemical pathways

Unit 4: Chemistry at work
-Industrial chemistry
-Supplying and using energy

 

[RANK 1]

is this prelim?

 

[Cupcake16XD]

is this prelim?

Units 1 and 2 are..><

 

[maths lover]

i dnt get why you multiplied the 83kj by the 0.01. can you please explain.

 

[someth1ng]

i'm lost aswell, what units do you use?

 

[someth1ng]

Okay, this is how it works I think
A=Delta

AH=-mCAT
-83000J*0.01=-100(4.18)AT
-830=-418 AT
AT=2

.`. new temperature=18+2=20C

The negative in -83 is because it is exothermic (given) so enthralpy so we know it is negative.

 

[goobi]

can anyone help with question 24 in this paper, my test it tomorrow and im not sure if i have the right answer.
http://exampapers.web.fc2.com/tests/hs/y11/chemistry/2008IndependentYearly.pdf
thankyou

Hope the solutions that I sent help

 

[someth1ng]

Hope the solutions that I sent help

...so what's the answer?

 

[someth1ng]

therefore ∆T= 0.83/(100 x 4.18 x 10^3)
= 1.986

What happened there? That equation isn't equal to 1.986?

 

[kwu1]

i dnt get why you multiplied the 83kj by the 0.01. can you please explain.

He multiplied by 0.01 because the 83kJ was per mol. We were told by the question that CaCl2 was 0.01 mole. If he didn't convert it, the units wouldn't have worked out.

 

[kwu1]

What happened there? That equation isn't equal to 1.986?

His solution is a bit weird. I think it is meant to be... Change in temperature = 0.83/(0.1 x 4.18) which gives you 1.986 degrees.

 

[someth1ng]

His solution is a bit weird. I think it is meant to be... Change in temperature = 0.83/(0.1 x 4.18) which gives you 1.986 degrees.

I figure out that you need to change everything to Joules not kJ.

I fixed my working from the other post so I now should have the right one

 

[RANK 1]

His solution is a bit weird. I think it is meant to be... Change in temperature = 0.83/(0.1 x 4.18) which gives you 1.986 degrees.

what are you on about? it says find the final temperature, given that the intial temperature is 18 so you plus 1.986 with 18