Question

In a lab experiment, a 10 ml sample of NaCl solution is poured into an evaporating dish with a mass of 24.10 g. The combined mass of the evaporating dish and NaCl solution is 36.15 g. After heating, the evaporating dish and dry NaCl have a combined weight of 25.50 g. What is the concentration of the HCl?

a. 1 M
b. 2 M
c. 0.5 M
d. 3 M

Answer 1

The concentration of the NaCl solution if after heating, the evaporating dish and dry NaCl have a combined weight of 25.50 g is 2 M (Option B).

Step-by-step explanation:

The problem you've presented involves finding the concentration of the NaCl solution after evaporation based on mass measurements before and after the heating process. To calculate the molarity of the original NaCl solution, we need to find the amount of NaCl present in the solution using the masses provided. Here's how you can calculate this:

First, determine the mass of NaCl alone by subtracting the mass of the empty evaporating dish (24.10 g) from the combined mass after evaporation (25.50 g). This gives you the mass of NaCl, which is

25.50 g - 24.10 g = 1.40 g.

Next, convert the mass of NaCl to moles using its molar mass (58.44 g/mol):

1.40 g / 58.44 g/mol = 0.02395 mol.

Finally, calculate the molarity of the NaCl solution using the initial volume of the solution (10 mL, or 0.010 L) by dividing the moles of NaCl by the volume in liters:

0.02395 mol / 0.010 L = 2.395 M.

Therefore, the concentration of the NaCl solution is approximately 2 M before evaporation (Option B).