What mass (in grams) of sodium chloride, NaCl, is needed to make 422. g of a 3.39%(m/m) NaCl solution?
(atomic masses: Na = 22.99, Cl = 35.45)
[(x grams solute/(grams solution)]*100 = %
Solve for grams solute.
442 g * 0.0339 = 14.98 g
I think you mis-read the problem. mass of the solution is 422g and not 442; otherwise, your procedure is ok.
To find the mass of sodium chloride needed to make a 3.39% (m/m) sodium chloride solution, we first need to understand what "3.39% (m/m)" means. "% (m/m)" is a mass/mass percent, which indicates the weight of the solute (sodium chloride) per 100 units of the solution's mass.
Here's how we can calculate it step by step:
Step 1: Convert the percentage to a decimal fraction:
3.39% = 3.39 / 100 = 0.0339
Step 2: Determine the mass of the solution:
Given that the mass of the solution is 422 g, we multiply it by the decimal fraction:
422 g * 0.0339 = 14.3218 g
Step 3: Calculate the mass of sodium chloride (NaCl):
The mass of sodium chloride is equal to the mass of the solution multiplied by the mass percent:
14.3218 g * 100 / (100 - 3.39) = 14.3218 g * 100 / 96.61
Step 4: Convert grams to moles:
To find the number of moles of sodium chloride, we need to divide the mass (in grams) by the molar mass (sum of atomic masses of Na and Cl).
The molar mass of NaCl = 22.99 g/mol (Na) + 35.45 g/mol (Cl) = 58.44 g/mol.
mol of NaCl = mass of NaCl / molar mass of NaCl
mol of NaCl = 14.3218 g / 58.44 g/mol
Step 5: Calculate the final mass of sodium chloride in grams:
To determine the mass of sodium chloride needed, we multiply the number of moles by the molar mass:
mass of NaCl = mol of NaCl * molar mass of NaCl
mass of NaCl = 14.3218 g / 58.44 g/mol * 58.44 g/mol
Calculating this yields the final answer.
It is important to note that in most cases, it is advisable to use a balance for accurate measurements and use precise molar masses from the periodic table for the calculations.