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Calculate the molarity of 5.0 g of NaOH in 750 mL of solution (atomic mass of NaOH is 39.9969 g/mol).

A. 0.00017 M
B. 6.67 M
C. 0.167 M


Sagot :

Sure! Let's solve the problem step-by-step:

1. Understand the given values:
- Mass of NaOH (solute): 5.0 grams
- Volume of the solution: 750 milliliters
- Atomic mass (molar mass) of NaOH: 39.9969 grams per mole

2. Convert the volume of the solution from milliliters to liters:
- Since there are 1000 milliliters in a liter, we convert 750 milliliters to liters:
[tex]\[ \text{Volume in liters} = \frac{750 \text{ mL}}{1000} = 0.75 \text{ L} \][/tex]

3. Calculate the number of moles of NaOH:
- Use the molar mass of NaOH to convert grams to moles:
[tex]\[ \text{Moles of NaOH} = \frac{\text{Mass of NaOH}}{\text{Molar mass of NaOH}} = \frac{5.0 \text{ g}}{39.9969 \text{ g/mol}} \approx 0.125 \][/tex]

4. Calculate the molarity:
- Molarity ([tex]\(M\)[/tex]) is defined as the number of moles of solute per liter of solution:
[tex]\[ \text{Molarity} = \frac{\text{Moles of NaOH}}{\text{Volume of solution in liters}} = \frac{0.125}{0.75} = 0.167 \text{ M} \][/tex]

Thus, the molarity of 5.0 grams of NaOH in 750 milliliters of solution is approximately 0.167 M/L.

Therefore, the correct answer is 0.167 M/L.