1. When interacting with water, lithium oxide forms hydroxide, we write down the corresponding reaction equation:
Li2O + H2O = 2LiOH;
2.Calculate the mass of hydroxide in the resulting solution:
m (LiOH) = w (LiOH) * m (solution) = 0.2 * 80 = 16 g;
3.Calculate the chemical amount of hydroxide:
n (LiOH) = m (LiOH): M (LiOH);
M (LiOH) = 7 + 16 + 1 = 24 g / mol;
n (LiOH) = 16: 24 = 0.6667 mol;
4.determine according to the ratio of the coefficients in the reaction equation the amount of reacted lithium oxide:
n (Li2O) = n (LiOH): 2 = 0.6667: 2 = 0.33335 mol;
5. find the mass of lithium oxide:
m (Li2O) = n (Li2O) * M (Li2O);
M (Li2O) = 7 * 2 + 16 = 30 g / mol;
m (Li2O) = 0.33335 * 30 = 10 g.
Answer: 10 g.
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