Question

A piece of Mg is dissolved in 40 ml of N/10 HCI completely. The excess of acid was neutralized by 15 ml of N/5 NaOH. The weight of Mg is

(A) 0.24 g
(B) 0.0129
(C) 0.024 g
(D) 0.40 g

Answer 1

To find the weight of Mg, we calculate the moles of Mg using the N/10 HCl and the volume of HCl, then calculate the moles of excess H+ by subtracting the moles of OH- added, and finally convert the moles of Mg to grams using the molar mass of Mg. The weight of Mg is approximately 0.024g, so the correct option is (C) 0.024 g.

Step-by-step explanation:

To find the weight of Mg, we can use the concept of neutralization reactions. First, we calculate the moles of Mg by using the N/10 HCl and the volume it reacts with: moles of Mg = (N/10 HCl)(volume of HCl). Next, we calculate the moles of excess H+ by subtracting the moles of OH- added from the moles of H+ needed to react with the Mg: moles of excess H+ = moles of H+ needed - moles of OH- added.

Finally, we convert the moles of Mg to grams by using the molar mass of Mg: weight of Mg = moles of Mg x molar mass of Mg.

Plugging in the given values, the weight of Mg is approximately 0.024g. Therefore, the correct option is (C) 0.024 g.