‘What mass of sodium hydroxide (NaOH; molar mass 40.0 g mol-I) is needed to make 100.0 mL of a 0.125 M NaOH solution? 0 A. 5.00 g B. 0.0500 g C.3.13 g D.0.500 g’
The Correct Answer and Explanation is:
To solve this, we can use the formula for molarity, which is:M=moles of solutevolume of solution in litersM = \frac{\text{moles of solute}}{\text{volume of solution in liters}}M=volume of solution in litersmoles of solute
Where:
- MMM is the molarity (moles per liter),
- The volume of the solution is given in liters,
- The moles of solute can be converted into grams using the molar mass of sodium hydroxide (NaOH).
Step 1: Calculate moles of NaOH needed
We are given:
- Molarity (M) = 0.125 M,
- Volume of solution (V) = 100.0 mL = 0.1000 L (since 1 L = 1000 mL).
We can calculate the moles of NaOH using the formula for molarity:moles of NaOH=M×V\text{moles of NaOH} = M \times Vmoles of NaOH=M×Vmoles of NaOH=0.125 mol/L×0.1000 L\text{moles of NaOH} = 0.125 \, \text{mol/L} \times 0.1000 \, \text{L}moles of NaOH=0.125mol/L×0.1000Lmoles of NaOH=0.0125 mol\text{moles of NaOH} = 0.0125 \, \text{mol}moles of NaOH=0.0125mol
Step 2: Convert moles of NaOH to grams
Next, we convert the moles of NaOH to grams using the molar mass of NaOH, which is 40.0 g/mol.mass of NaOH=moles of NaOH×molar mass of NaOH\text{mass of NaOH} = \text{moles of NaOH} \times \text{molar mass of NaOH}mass of NaOH=moles of NaOH×molar mass of NaOHmass of NaOH=0.0125 mol×40.0 g/mol\text{mass of NaOH} = 0.0125 \, \text{mol} \times 40.0 \, \text{g/mol}mass of NaOH=0.0125mol×40.0g/molmass of NaOH=0.500 g\text{mass of NaOH} = 0.500 \, \text{g}mass of NaOH=0.500g
Final Answer:
The mass of NaOH needed to prepare 100.0 mL of a 0.125 M NaOH solution is 0.500 g.
So, the correct answer is D. 0.500 g.
