calculate the amount of water in grams that must be added to 5.00 grams of urea (NH2)2 CO in the preparation of a 16.2 percent by mass, and 26.2 grams of MgCl2 in the preparation of a 1.5 percent by mass solution.
% w/w = (grams solute/g solution)*100
% = [grams solute/(g solute + g solvent)]
% = [5 g urea/5 g urea + g solvent)]*100 = 16.2
25.86g
To solve this problem, we need to find the amount of water needed to prepare a 16.2% by mass solution of urea (NH2)2CO and the amount of water needed to prepare a 1.5% by mass solution of MgCl2.
1. Determine the mass of urea needed:
Since we have 5.00 grams of urea, we can calculate the mass of urea needed using the formula:
Mass of urea = Mass of solution × Percent of urea
Since we need a 16.2% by mass solution, the mass of the solution can be calculated as:
Mass of solution = Mass of urea / (Percent of urea / 100)
Mass of solution = 5.00 g / (16.2 / 100) = 30.86 g
2. Determine the mass of water needed:
To prepare a 16.2% by mass solution, we subtract the mass of urea (NH2)2CO from the mass of the solution:
Mass of water = Mass of solution - Mass of urea
Mass of water = 30.86 g - 5.00 g = 25.86 g
Therefore, in the preparation of a 16.2% by mass solution, you need to add 25.86 grams of water to 5.00 grams of urea (NH2)2CO.
3. Calculate the mass of MgCl2 needed:
Similarly, we can calculate the mass of MgCl2 needed to prepare a 1.5% by mass solution using:
Mass of MgCl2 = Mass of solution × Percent of MgCl2
Since we need a 1.5% by mass solution, the mass of the solution can be calculated as:
Mass of solution = Mass of MgCl2 / (Percent of MgCl2 / 100)
Mass of solution = 26.2 g / (1.5 / 100) = 1,746.67 g
4. Determine the mass of water needed:
To prepare a 1.5% by mass solution, we subtract the mass of MgCl2 from the mass of the solution:
Mass of water = Mass of solution - Mass of MgCl2
Mass of water = 1,746.67 g - 26.2 g = 1,720.47 g
Therefore, in the preparation of a 1.5% by mass solution, you need to add 1,720.47 grams of water to 26.2 grams of MgCl2.
To calculate the amount of water in grams needed to prepare a solution with a given percentage by mass, we need to determine the mass of solute and the mass of the resulting solution.
Let's start with the first part of the question, the preparation of a 16.2% urea solution.
1. Determine the mass of urea needed:
- Given that we have 5.00 grams of urea (NH2)2CO.
2. Determine the mass of the resulting solution:
- We want a 16.2% solution, which means 16.2 grams of urea per 100 grams of solution.
- Let's assume we want to prepare a 100-gram solution.
To figure out how much water we need, we subtract the mass of urea from the mass of the solution:
Mass of water = Mass of solution - Mass of urea
Mass of solution = 100 grams
Mass of urea = 5.00 grams
Mass of water = 100 g - 5.00 g = 95.00 grams
Therefore, you need to add 95.00 grams of water to 5.00 grams of urea to prepare a 16.2% urea solution.
Moving on to the second part, the preparation of a 1.5% MgCl2 solution:
1. Determine the mass of MgCl2 needed:
- Given that we have 26.2 grams of MgCl2.
2. Determine the mass of the resulting solution:
- We want a 1.5% solution, which means 1.5 grams of MgCl2 per 100 grams of solution.
- Let's assume we want to prepare a 100-gram solution.
To determine the mass of water needed, we subtract the mass of MgCl2 from the mass of the solution:
Mass of water = Mass of solution - Mass of MgCl2
Mass of solution = 100 grams
Mass of MgCl2 = 26.2 grams
Mass of water = 100 g - 26.2 g = 73.8 grams
Therefore, you need to add 73.8 grams of water to 26.2 grams of MgCl2 to prepare a 1.5% MgCl2 solution.