Final answer:
To maintain the same mixture ratio, 3.5 grams of sodium chloride should be mixed with 175 millilitres of water.
Step-by-step explanation:
To maintain the same mixture ratio, we need to find out how much sodium chloride should be mixed with 175 millilitres of water. First, let's calculate the ratio of sodium chloride to water in the initial mixture. Dianna mixed 1.5 grams of sodium chloride with 75 millilitres of water, so the ratio is 1.5 grams / 75 millilitres = 0.02 grams per millilitre. Now, we can calculate the amount of sodium chloride needed for 175 millilitres of water. 0.02 grams/millilitre * 175 millilitres = 3.5 grams of sodium chloride.