What is the calculation to work out a dilution series?
C1V1=C2V2
You’re asked to make up a 30% dilution of a 1moldm^-3 sucrose stock solution. Describe how a 50cm^3 solution of this dilution would be made.
C1V1=C2V2
1x?=0.3x50
1x?=15
?=15
A stock solution is 1moldm^-3 sucrose. Describe how a 50cm^3 solution of 0.6moldm^3 sucrose can be made using this stock solution
C1V1=C2V2
1x?=0.6x50
1x?=30
?=30
What’s an advantage of using small pieces of potato?
Large surface area to volume ratio means faster rate of osmosis so you can observe the change more quickly
What happens to a cell in a low concentration solution? What about a high one?
Low - turgid, high - plasmolysed
What are some limitations of the investigation? What are some ways to reduce this?
1) evaporation of solution - use bungs
2) only a few molarities of the solution used, test more concentrations
What are advantages of doing repeats?
1) Anomalies can be taken into account (don’t accept removed or prevented)
2) reliable mean can be calculated
Why peel the potato?
The skin is impermeable to water
Why is the same potato variety used?
Different varieties have different sucrose concentrations
Why is there eventually no change in mass of potato?
Equilibrium is reached so net movement of water into/ out of the potato means constant mass
What organism is often used in experiments to measure membrane permeability through the release of its pigment?
Beetroot
