Determination of the salinity of three estuarine water samples

[FBarrett]

Hi,

 

This is my first post and i'm stuck on this question.

 

I cant figure out how to determine the concentration of unknown water samples using known specific gravities.

 

What methods i.e formulas do i need to use.

Any help would be appreciated.

 

Thanks.

 

 

Determination of the salinity of three estuarine water samples.pdf

[hypervalent_iodine]

Where are you stuck exactly? Do you understand how to interpret the graph and the equation given?

[studiot]

Further do you know why you are given three samples but only asked to calculate the concentration for 2 of them?

 

R² is a statistical measure of the 'quality' of the straight line on the graph.

 

https://www.google.co.uk/search?q=R%5E2+in+regression+analysis&ie=utf-8&oe=utf-8&client=firefox-b-ab&gfe_rd=cr&ei=GBJkWaD9D8bU8gfcg5_oBw

[hypervalent_iodine]

Further do you know why you are given three samples but only asked to calculate the concentration for 2 of them?

 

R² is a statistical measure of the 'quality' of the straight line on the graph.

 

https://www.google.co.uk/search?q=R%5E2+in+regression+analysis&ie=utf-8&oe=utf-8&client=firefox-b-ab&gfe_rd=cr&ei=GBJkWaD9D8bU8gfcg5_oBw

 

 

I took it as a typo in the question. The R² value isn't really relevant to answering the question.

[FBarrett]

Thank you all for your help.

I think i managed to get it done.

This is my answers.

Unknown A = 1.007

y = 0.0061X + 0.9989

1.007 = 0.0061X + 0.9989

1.007 - 0.9989 = 0.0061X

X = 1.007 - 0.9989 / 0.0061 = 1.3279 PPM

 

 

Unknown B = 1.015

y = 0.0061X + 0.9989

1.015 = 0.0061X + 0.9989

1.015 - 0.9989 = 0.0061X

X = 1.015 - 0.9989 / 0.0061 = 2.6393 PPM

 

 

Unknown C = 1.018

y = 0.0061X + 0.9989

1.018 = 0.0061X + 0.9989

1.018 - 0.9989 = 0.0061X

X = 1.018 - 0.9989 / 0.0061 = 3.311 PPM

 

Any guidance on where i went wrong would be greatly appreciated.

 

Thanks

[hypervalent_iodine]

Your units are off, but calculations are correct. You calculated the % since that is the unit of the x axis, not ppm. They're not the same thing, so you'll need to convert.