Empirical and molecular formulas

Answer Key - Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   A lab analysis of a glucose sample finds 24.02 g of carbon. Carbon is 12.01 g/mol. How many moles of carbon atoms is that, to 0.01 mol, Bo?

   2 mol
2. 2.

   A glucose sample holds 24.02 g C, 4.04 g H and 32.00 g O, which is 2 mol C, 4 mol H and 2 mol O. What is its empirical formula, Kira?

   • C₂₄H₄O₃₂
   • C₂H₄O₂
   • CH₂O
3. 3.

   A sample holds 24.02 g C, 4.04 g H and 32.00 g O. Why can't you read the formula from the grams, Luz?

   • You can, after rounding each mass to a whole number
   • You can: the formula is C₂₄H₄O₃₂
   • A formula counts atoms, so change grams to moles first
4. 4.

   Moles in a glucose sample: C 2, H 4, O 2. Divide each by the smallest, 2. Which ratio results, Milo?

   • 1 C : 2 H : 1 O
   • 2 C : 4 H : 2 O
   • 1 C : 1 H : 1 O
5. 5.

   Which of these formulas can be simplified, Noah?

   • C₆H₁₂O₆, glucose
   • C₁₂H₂₂O₁₁, table sugar
   • H₂O, water
6. 6.

   Why is CO₂ already its own empirical formula, Pia?

   • 1 and 2 share no common factor but 1
   • It has fewer than three elements
   • Gases have no empirical formulas
7. 7.

   Which mole ratio gives the empirical formula CH₂O, Ren?

   • 1 mol C, 1 mol H, 2 mol O
   • 3 mol C, 6 mol H, 3 mol O
   • 2 mol C, 2 mol H, 1 mol O
8. 8.

   Glucose's empirical formula is CH₂O, and n = 6. What is its molecular formula, Tala?

   • C₆H₁₂O₆
   • CH₂O₆
   • C₆H₂O
9. 9.

   CH₂O has a mass of 30.03 g/mol, and glucose 180.18 g/mol. How many CH₂O units make one glucose, Zee?

   • 150.15, from 180.18 − 30.03
   • 6, since 180.18 ÷ 30.03 = 6
   • 0.17, from dividing 30.03 by 180.18
10. 10.

    Which shows how to get a molecular formula from an empirical one, Ari?

    • Multiply just the first subscript by n
    • Multiply each subscript by n
    • Add n to each subscript