Why does adding lemon juice to blueberry smoothie make it change colour from purple to pink

Yasmin's teacher asks her to make a supersaturated saline solution. her teacher tells her that the solubility of the salt is 360 g/l at room temperature (25 °c). how can yasmin make a supersaturated saline solution? she can add 380 g of salt to 1 l of hot water (75 °c) and stir until all the salt dissolves. then, she can carefully cool the solution to room temperature (25 °c). she can add 360 g of salt to 1 l of room temperature water (25 °c) and stir the solution until all the salt dissolves. she can add 380 g of salt to 1 l of cold water (5 °c) and stir the solution until most of the salt dissolves. then, she can carefully heat the solution to room temperature (25 °c). she can add 380 g of salt to 1 l of room temperature water (25 °c) and let the solution sit for 24 hours, so the salt dissolves.