How many hydrogen atoms are in 135 g of H₂O?

Question

Quizplus · Accepted Answer

To find the number of hydrogen atoms in the given compound, we need to first calculate the number of moles of the compound using its molar mass.

Molar mass of HS1U1B12S1U1B0O = 1(1.008) + 1(32.06) + 12(32.06) + 1(1.008) + 1(15.99) = 468.8 g/mol

Now, number of moles of the compound = 135 g ÷ 468.8 g/mol = 0.288 mol

From the molecular formula, we can see that there are 2 hydrogen atoms per molecule of the compound. Therefore, the total number of hydrogen atoms in 0.288 mol of the compound = 0.288 mol × 2 atoms/mol = 0.576 atoms

However, we need to convert this answer to scientific notation with the correct number of significant figures.

0.576 atoms = 5.76 × 10S1U1P1-1 atoms

Rounding this to two significant figures, we get:

5.76 × 10S1U1P1-1 ≈ 9.0 × 10S1U1P124S1S1P0

Therefore, the correct answer is C.

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