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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ineedhelp10 on August 23, 2010, 10:52:08 AM

Hi i want to understand how to work out the solubility in grams of SO2 in water under the following conditions:
500ml of H20
Assume equilibrium conditions, and ignore any reaction with water.
external atmosphere contains 5% SO2.
so firstly i want to know how and where to look up the henry's law constant?
secondly i would like an explanation of the math involved in the calculations and finally want to end up with the answer in grams.
Thanks for your time

Hi i want to understand how to work out the solubility in grams of SO2 in water under the following conditions:
[...]
so firstly i want to know how and where to look up the henry's law constant?
secondly i would like an explanation of the math involved in the calculations and finally want to end up with the answer in grams.
Didn't you forget something, perchance? ;D
We want (nay "We'd like") to see you attempts before helping you... as for the constant try looking it up on the CRC Handbook or similar texts.

The reason i haven't shown you my attemps is that i dont know where to start. for instance i found a pdf of the henry's law constants. this is what it says:
sulfur dioxide 1.2 3200 Sillen and Martell [1964] X 1
SO2 1.2 3100 Hales and Sutter [1973] c
[7446095] 1.1 Liss and Slater [1974] c
1.2 3100 Smith and Martell [1976] X 1
1.4 2800 Wilhelm et al. [1977] L
1.2 3000 Edwards et al. [1978] L
1.2 Durham et al. [1981] C
1.2 3100 Chameides [1984] T
1.2 3100 Hoffmann and Jacob [1984] ? 4
1.2 3200 Jacob [1986] C
1.2 3100 Pandis and Seinfeld [1989] C
1.5 2900 Dean [1992] ? 2
1.2 Maahs [1982] X 11
1.2 3200 Maahs [1982] X 1
1.4 2900 Lide and Frederikse [1995] L
1.3 2800 Kavanaugh and Trussell [1980] X 3
so to start with i have 16 different constants. then to find the henry's law equation
i found four differing ones. then i dont understand what all the symbols mean. i think K is the actual constant used. H? C? P? X?
i dont require the answer to the question posed. a worked example would be very beneficial though. i would just like to understand the maths involved. what a constant would look like? is it 1.1 or 2900? then an insight to the equation i should use and the meanings of the symbols.
thanks again

First column contains values of the constant (obviously 1.2 is the dominating one, they differ as they all have some experimental errors), the other one shows how the constant change with the temperature.
Same document contains Henry's law in the form that was used when calculating the constant value (equation 1). k_{H} is the constant itself, c_{a} is concentration, p_{g} is pressure.

kH
def = ca/pg
so kH = 1.2
ca = what im looking for i think
pg = STP = 100kPa
so 1.2 = ca/100
120?

120 of what? Do you know what units your concentration is in?

the sad thing is. no. however i did find an answer to a similar question for h2s and added in my bits. is this anywhere near correct?
Constant used = 1.2
[SO2] = p (SO2) * KH
[SO2] = 0.001 * 1.2
= 0.0012 mol.L1
Ans/2 = 0.0006 mol per 500ml
= 0.0192g 1 mol SO2 = 32g

Please list units you are using, without them numbers don't have any sense.
It is like stating you are 12.3 high, or your room surface is 23.

im sorry; this is why i need help. the 1.2 i took from a pdf under colum
k
H
[M/atm].
so the constant is 1.2. of what i haven't the foggiest. i give up.
thanks anyway