A solution of concentrated NaOH is 16.7M. If the density of the solution is 1.02 g/mL, what is the percent by mass of NaOH?
I have tried different calculations and molarity and % but im not catching on at all
I have always used this one. Works every time.
1.02 g/mL x 1000 mL x (%/100) x (1/molar mass NaOH) = M
You can do it piecemeal if you wish.
M = mols/L. You know M and 1L, solve for mols.
grams NaOH = mols x molar mass gives you grams solute.
density of the 1 L gives you grams of the solution.
(grams solute/grams solution)*100 = %
To find the percent by mass of NaOH in the solution, you need to understand the relationship between molarity, density, and percent by mass.
Molarity (M) is defined as the number of moles of solute per liter of solution. In this case, the molarity of the NaOH solution is given as 16.7 M.
Density is the mass of a substance per unit volume. In this case, the density of the NaOH solution is given as 1.02 g/mL.
Percent by mass is the mass of solute per 100 grams of solution. To calculate the percent by mass of NaOH, we need to first determine the mass of NaOH in a given volume of solution.
Here's how you can approach this problem step by step:
Step 1: Convert the given density into grams per liter (g/L) since the molarity is given in moles per liter (mol/L).
Given: Density = 1.02 g/mL
To convert g/mL to g/L, multiply the given density by 1000:
Density = 1.02 g/mL x 1000 mL/L = 1020 g/L
Now you have the density in grams per liter (g/L).
Step 2: Calculate the moles of NaOH in the solution using molarity and volume.
Given: Molarity = 16.7 M
Since molarity is defined as moles of solute per liter of solution, you need to determine the volume of the solution in liters.
Step 3: Determine the mass of NaOH using its molar mass.
The molar mass of NaOH is 22.99 g/mol (for Na) + 16.00 g/mol (for O) + 1.01 g/mol (for H) = 39.00 g/mol.
Multiply the moles of NaOH obtained in step 2 by its molar mass to determine the mass of NaOH.
Step 4: Calculate the percent by mass of NaOH.
To calculate the percent by mass, divide the mass of NaOH by the mass of the entire solution (including NaOH) and multiply by 100.
Mass of NaOH / Mass of solution × 100
The mass of the solution can be obtained by multiplying the given density by the volume of the solution.
Finally, you can substitute the values to get the percent by mass of NaOH in the solution.
I hope this explanation helps you understand the steps involved in solving the problem.