7) 7) What is the mass percent of oxygen in sodium oxide? SHOW ALL WORK A) 74.2

Question

7) 7) What is the mass percent of oxygen in sodium oxide? SHOW ALL WORK A) 74.2 B) 25.8 C) 37.1 8) Bauxite is an ore that contains the element aluminum. If you obtained 108 grams of aluminum from 8) an ore sample that initially weighed 204 grams, what is the mass percent bauxite ore? SHOW ALL WORK of aluminum in this A) 52.9 B) 47.1 C) 0.53 D) 15.6 9) When elements combine to form compounds A) their properties change completely B) their properties do not change. C) their properties are completely random. D) their properties are an average of all elements in the compound. E) none of the above 10) What is the correct formula for a compound that has three oxygen atoms and one sulfur atom? 10) B) SO3 C) so3 D) 30S E) none of the above 11) How many hydrogen atoms are in 35.0 grams of hydrogen gas? SHOW ALL WORK 1025 A) 2.09 1025 B) 105 C) 4.25 1025 D) 2.12 1025 12) How many moles of iron are contained in 1.75 kg of iron? SHOW ALL WORK 12) A) 3.13 x 10-2 B) 3.13 x 10-4 C) 313 D) 3.13 x 104

Explanation / Answer

Ans 7 : B) 25.8 %

The formula of sodium oxide is Na2O

The molar mass of the compound is 61.9789 g/mol

The amount of oxygen in it is 15.999 g/mol

So the mass percent of oxygen = (15.999 / 61.9789) x 100

= 25.8 %

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