Answer:

Explanation:
Hello.
In this case, given the chemical reaction, we can compute the grams of oxygen by using the 98.2 g of water via the 2:1 mole ratio between them, the molar mass of water that is 18.02 g/mol, the molar mass of gaseous oxygen that is 32.00 g/mol and the following stoichiometric procedure relating the given information:

In which the result is displayed with three significant figures because the given mass of water 98.2 g, has three significant figures too.
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Answer:
not a reason? if you ask a reason ,i can say An actual yield is the mass of a product actually obtained from the reaction. It is usually less than the theoretical yield. The reasons for this include:
-->incomplete reactions, in which some of the reactants do not react to form the product
practical losses during the experiment
->side reactions (unwanted reactions that compete with the desired reaction)
->reversible reactions
->impurities in reactants
but you asked for not reason then it can be anything lul, like balanced chemical equation, rate of reaction and etc etc ✌️;)
Explanation:
5 trial, had an average destiny of 7.40. g/cm
Elements in the third row can break the octet rule