Question

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution; the mass of sodium hydroxide left unreacted is equal to ______.

पर्याय

• Zero mg

• 200 mg

• 750 mg

• 250 mg

Answer 1

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution; the mass of sodium hydroxide left unreacted is equal to 250 mg.

Explanation:

Number of mole of NaOH in 1 g = `1/40`

= 0.025 mole

Number of mole of HCl in 25 mL = `(0.75 xx 25)/1000`

= 0.01875

Number of moles of NaOH unreacted = 0.025 − 0.01875

= 0.00625

Mass of NaOH unreacted = Number of moles unreacted × Molar mass

= 0.00625 × 40

= 0.25g

= 250 mg