sac 1!! - potatoes! hellp =(

[Lesliel1]

Hi,
I did a prac sac with potatoes where there are 6 test tubes with different salt concentrations- 0%, 0.5%, 1%, 5% and 10%. Then we had to find out the change in mass of the potatoes after we soaked them in the solutions for 30 mins.
then there was a question in the prac sac asking:

if the salt concentration of the potato cell was aprox. 0.9%, what would be the control?
i put in the one with distilled water (0%) and i dont know if it is right or wrong =(

could someone please tell me?

[Russ]

the control would be the one closest to the intracellular concentration (in this case, the 1% solution).
Distilled water will still result in osmotic movement of water due to solute imbalance

[pi]

i put in the one with distilled water (0%) and i dont know if it is right or wrong =(

could someone please tell me?

You mentioned 6 test tubes, but only gave 5 concentrations. What was in the other test-tube? (although Russ is probably right)

[Lesliel1]

2%,
 so im wrong? =( omggg =( but its still 0.9% not 1% lol :S

[pi]

2%,
 so im wrong? =( omggg =( but its still 0.9% not 1% lol :S

1% is the closest. Go back to the definition of osmosis, and you'll see that the least mass lost/gained will be in this one. Of course the ideal control would have the same salt concentration as the potato. Its a tough question though.

[HERculina]

YOU HAD THE SAME PRAC AS ME :O
our solutions were 0%, 0.5%, 1%, 2.5%, 5% and 20% salt concentrated
theres a write up for this prac in heinemann workbook pg 37 btw