First, calculate the amount fo Na2O that should be produced with the given amount of sodium using proper dimensional analysis and the balanced chemical reaction,
theoretical amount of Na2O = (54.1 g of Na)(1 mol Na/23 g Na)(2 mos Na2O/4 mols Na)(62 g Na2O/ 1mol Na2O)
theoretical amount of Na2O = 72.9 g of Na2O
Calculation of percent yield,
% yield = (61.8 g Na2O) / (72.9 g of Na2O) x 100%
% yield = 84.75%
Answer: 84.75%