What mass of substance would be needed to prepare these solutions:
1) 400ml (cm3) at 5% weight/volume
2) 50ml (cm3) of NAOH at 10% weight/volume
To determine the mass of a substance required to prepare a solution, you need to know the desired concentration (expressed as a weight/volume percentage) and the volume of the solution.
To calculate the mass, you can use the formula:
Mass = (Volume * Concentration) / 100
Let's use this formula to calculate the mass for each of the given solutions:
1) 400ml (cm3) at 5% weight/volume:
Mass = (400 * 5) / 100
Mass = 20 grams
Therefore, you would need 20 grams of the substance to prepare 400ml of a 5% weight/volume solution.
2) 50ml (cm3) of NAOH at 10% weight/volume:
Mass = (50 * 10) / 100
Mass = 5 grams
Thus, you would require 5 grams of NAOH to prepare 50ml of a 10% weight/volume solution.