A 15.0% (by mass) NaCl solution is available.. Determine what mass of solution should be used to obtain
a. 2.50 mole of NaCl
b. 25.0 g/mol of NaCl
To determine the mass of solution needed to obtain a specific amount of NaCl, we need to use the molar mass of NaCl and the concentration of the solution.
a. To obtain 2.50 moles of NaCl:
Step 1: Find the molar mass of NaCl.
The molar mass of NaCl is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl):
Na: 22.99 g/mol
Cl: 35.45 g/mol
Molar mass of NaCl = 22.99 g/mol + 35.45 g/mol = 58.44 g/mol
Step 2: Calculate the mass of NaCl needed.
Mass = moles × molar mass
Mass = 2.50 mol × 58.44 g/mol = 146.1 g
Therefore, to obtain 2.50 moles of NaCl, you would need 146.1 grams of the solution.
b. To obtain 25.0 grams of NaCl:
Step 1: Determine the molar mass of NaCl (already calculated as 58.44 g/mol).
Step 2: Calculate the moles of NaCl from the given mass.
Moles = mass / molar mass
Moles = 25.0 g / 58.44 g/mol = 0.428 mol
Step 3: Calculate the mass of the solution needed.
Mass = moles / (concentration in decimal form)
Mass = 0.428 mol / (0.15) = 2.85 g
Therefore, to obtain 25.0 grams of NaCl, you would need approximately 2.85 grams of the solution.
To determine the mass of solution needed to obtain a certain amount of NaCl, we can use the formula:
Mass of solution = (moles of NaCl / concentration of NaCl) x 100
Where:
- Moles of NaCl is the desired amount of NaCl in moles
- Concentration of NaCl is the percentage of NaCl in the solution, which is 15.0% in this case
a. To find the mass of solution needed to obtain 2.50 moles of NaCl:
Mass of solution = (2.50 moles / 15.0%) x 100
First, we need to convert the percentage to a decimal by dividing it by 100:
Mass of solution = (2.50 moles / 0.150) x 100
Now we can calculate:
Mass of solution = 16.67... x 100
Mass of solution ≈ 1667 grams or 1.67 kilograms (rounded to two decimal places)
Therefore, approximately 1667 grams or 1.67 kilograms of solution should be used to obtain 2.50 moles of NaCl.
b. To find the mass of solution needed to obtain 25.0 grams of NaCl:
We can use the same formula:
Mass of solution = (25.0 grams / 15.0%) x 100
Converting the percentage to a decimal:
Mass of solution = (25.0 grams / 0.150) x 100
Calculating:
Mass of solution = 166.67... x 100
Mass of solution ≈ 16667 grams or 16.67 kilograms (rounded to two decimal places)
Therefore, approximately 16667 grams or 16.67 kilograms of solution should be used to obtain 25.0 grams of NaCl.
A 15.0% NaCl solution means 15.0 g NaCl in 100 g solution. You want 2.50 moles NaCl.
1 mole NaCl is 58.44 grams so 2.50 moles = 2.50 x 58.44 = ?? grams (about 145 g or so) but you need to do it more accurately.
So you want to take 100 g soln x (145/15.0) = ??
Check my thinking.