Consider the mass of lithium that needs to be added to the required amount of water to obtain an aqueous

Consider the mass of lithium that needs to be added to the required amount of water to obtain an aqueous solution of lithium hydroxide weighing 8.50 g with a mass fraction of LiOH equal to 7.50%.

The mass of lithium hydroxide is 8.5 g.

The mass fraction of lithium hydroxide is 7.5%.

Let’s determine the mass of lithium, which has reacted with water.

2Li + 2HOH = 2LiOH + H2.

Let us first determine the mass of lithium hydroxide.

W = m r.v / m r-ra * 100%.

m p.w = 8.5 * 0.075 = 0.6375 g.

Further, according to the reaction equation, we determine the mass of lithium, which entered into the reaction.

Determine the molar mass of lithium and lithium hydroxide.

M (Li) = 7 g / mol.

M (LiOH) = 24 g / mol.

Let’s determine the mass of lithium.

X g of lithium – 0.6375 g of lithium hydroxide.

2 * 7 g / mol – 2 * 24 g / mol.

X = 2 * 7 * 0.6375 / (2 * 24) = 0.2 g.

Answer: the mass of lithium is 0.2 g.