AQA Alevel Biology 2019 paper 1

Hey so I need help for question 8.2 on paper 1 biology 🥲
I don’t understand how they got the answer 0.07 moldm-3. Pls help 🙏🏼

Reply 1

3908

It’s like ratios.

If -1.95 MPa = 0.04 mol dm

And you want to find the mol/dm that is associated with the MPa in the question (-3.41)

You divide 3.41 by 1.95 to get the multiplication factor, or by how much 3.41 is greater than 1.95
-> 3.41/1.95 = 1.794736842105263
(Don’t use the - in the calculations, it will mess it up)

Then now you know the difference just multiply it by 0.04
-> 1.794736842105263 x 0.04 = 0.069948717948718
-> round to 2dp = 0.07

Reply 2

BlueChicken

It tells you there is a linear relationship between sodium chloride concentration and water potential. This means NaCl concentration * X = water potential (or, if you like, NaCl concentration/water potential = a constant; it doesn’t matter, as the relationship is linear, you just need to make sure you keep your equation consistent). Use data in table to work out X. Then rearrange equation and put in X and water potential given to determine sodium chloride concentration.