How many moles of sodium chloride (NaCl) solute are in 155 grams of an 85.5 percent by mass solution?
155 x 0.855 = ?g NaCl
moles = grams/molar mass
To find the number of moles of sodium chloride (NaCl) solute in the given solution, we need to use the concept of molar mass and percent composition.
1. Determine the molar mass of sodium chloride (NaCl):
The molar mass of Na is approximately 22.99 g/mol, and Cl is approximately 35.45 g/mol.
Thus, NaCl has a molar mass of 22.99 + 35.45 = 58.44 g/mol.
2. Calculate the mass of NaCl solute in the solution:
Since the given solution is 85.5 percent by mass, this means that 85.5 grams of the 100-gram solution is NaCl.
Therefore, the mass of NaCl solute is calculated as (85.5 percent / 100 percent) x 155 grams = 132.525 grams.
3. Convert the mass of NaCl solute to moles:
Divide the mass of NaCl solute by its molar mass:
Moles = (mass / molar mass)
Moles of NaCl = 132.525 grams / 58.44 g/mol
Use a calculator to compute the value: Moles of NaCl ≈ 2.269 mol
So, there are approximately 2.269 moles of sodium chloride (NaCl) solute in 155 grams of an 85.5 percent by mass solution.