Ambiguous question: (1 Viewer)

[The Bograt]

A student wanted to determine if a water sample was sea water or fresh water. Which of the following tests would most readily distinuguish between sea water and fresh water?
A. Hardness
B. Turbidity
C. Total Dissolved Solids
D. Dissolved Oxygen and biochemical oxygen demand

This is in the Catholic Schools paper, and was also in my trial.
The Catholic answer is C - TDS
The trial answer was A - Hardness


Hardness would be the easiest to test, since you just see how well each of them create a lather

TDS is the obvious answer, since the sea water would have a great deal more dissolved solids (especially NaCl)

So which test will most readily distinguish between the two?

 

[Tommy_Lamp]

i think TDS as hardness relies on the prescence of certain ions (e.g. Mg and Ca) which may not be present in that specific sample. whereas you are ensured of NaCl if it is sea-water and not much TDS if it is fresh water. Also both the Fresh water and Sea water could contain the said ions.

i might be wrong

 

[nesstar]

Hardness would be the easiest to test, since you just see how well each of them create a lather

TDS is the obvious answer, since the sea water would have a great deal more dissolved solids (especially NaCl)

So which test will most readily distinguish between the two?

I think TDS is not just most obvious but also the easiest/quickest...providing u have a TDS meter...

The conflicting answers confirm its ambiguity - i wouldn't worry too much about it

 

[tina_goes_doo]

Yeah i would go for TDS too.

 

[mervvyn]

Same, TDS seems to be the obvious choice... what tommy said covers it i think.

 

[The Bograt]

Alrighty thanks guys I'll stick with TDS