It seems that you have missed the necessary options for us to answer this question, but anyway here is the answer. William adds two values, following the rules for using significant figures in computations. He should write the sum of these two numbers by using the same number of decimal places as the least precise value. Hope this helps.
The Molar mass of an atom corresponds directly with its atomic mass on the periodic table.
Answer:
https://www.quora.com/The-following-chemical-reaction-shows-the-decomposition-of-water-to-form-hydrogen-gas-and-oxygen-gas-2H2O-I-produces-2H2-g-O2-g-if-10-0-grams-of-water-reacted-and-you-found-1-11-grams-of-H2-formed-how-many-of-O2
Explanation: i hope ths helps you