How much sodium hydroxide is required to make 250 cm² of a 0.1 molar solution?

 How much sodium hydroxide is required to make 250 cm² of a 0.1 molar solution?

[Na = 23,; O= 16; H= 1]

A. 10.0g

B. 4.0 g

C. 2.0g

D. 1.0g

E. 0.1g

The correct answer is D.

Solution:

To calculate the amount of sodium hydroxide (NaOH) needed to make a 250 cm³ of a 0.1 molar solution, we need to use the formula

moles = molarity × volume (in dm³)

First, we need to convert the volume from cm³ to dm³ 

To do that we divide by 1000 to get it in dm'3

250 cm³ = 250 / 1000 = 0.25 dm³

Now, we can calculate the moles of NaOH as follows:

moles = 0.1 mol/dm³ × 0.25 dm³ = 0.025 moles

Next, we need to find the molar mass of NaOH

Molar mass of NaOH = Na + O + H = 23 + 16 + 1 = 40 g/mol

Finally, we can calculate the mass of NaOH required:

mass = moles × molar mass = 0.025 moles × 40 g/mol = 1.0 g

So, the correct answer is Option D. 1.0 g of sodium hydroxide is required to make a 250 cm³ of a 0.1 molar solution.

SOURCE: NECO CHEMISTRY 2001 QUESTION 13