Question 8. The mass of NaOH required to prepare 250~cm^{3} of 0.1M NaOH is?
(A) 10g (B) 4g (C) 40g (D) 1g
In order to calculate the mass of NaOH required to prepare a certain volume of a given concentration, we can use the formula:
Molarity (M) = moles of solute (NaOH) / volume of solution (in liters)
First, we need to convert the given volume from cubic centimeters (cm^3) to liters:
250 cm^3 = 250/1000 = 0.25 liters
Now we can rearrange the formula to solve for moles of NaOH:
moles of solute (NaOH) = Molarity (M) x volume of solution (in liters)
moles of solute (NaOH) = 0.1 M x 0.25 L = 0.025 moles
Finally, we can calculate the mass of NaOH using its molar mass:
mass of NaOH = moles of NaOH x molar mass of NaOH
The molar mass of NaOH is 23g/mol + 16g/mol + 1g/mol = 40g/mol
mass of NaOH = 0.025 moles x 40 g/mol = 1g
Therefore, the mass of NaOH required to prepare 250 cm^3 of 0.1M NaOH is 1g. The correct answer is option (D) 1g.