Ask Question
9 March, 07:54

Naphthalene, commonly found in moth balls, is composed of 93.7% carbon and 6.3% hydrogen. The molar mass of naphthalene is 128 g/mol. Determine the empirical and molecular formulas of naphthalene.

+5
Answers (2)
  1. 9 March, 08:17
    0
    The empirical formula is C5H4

    The molecular formula is C10H8

    Explanation:

    Step 1: Data given

    Suppose the mass = 100 grams

    Naphthalene contains:

    93.7 % C = 93.7 grams

    6.3 % H = 6.3 grams

    atomic mass of C = 12.01 g/mol

    atomic mass of H = 1.01 g/mol

    Molar mass of naphthalene = 128 g/mol

    Step 2: Calculate moles

    Moles = mass / molar mass

    Moles C = 93.7 grams / 12.01 g/mol

    Moles C = 7.80 moles

    Moles H = 6.3 grams / 1.01 g/mol

    Moles H = 6.24 moles

    Step 3: Calculate mol ratio

    We divide by the smallest amount of moles

    Moles C: 7.80 moles / 6.24 moles

    Moles C: 1.25

    Moles H: 6.24 moles / 6.24 moles

    Moles H: 1

    The empirical formula is C5H4

    The molecular weight is 64.09 g/mol

    128 g/mol / 64.09 g/mol = 2

    We have to multiply the empirical formula by 2

    2 * (C5H4) = C10H8

    The molecular formula is C10H8
  2. 9 March, 08:20
    0
    Molecular formula naphthalene → C₁₀H₈

    Empirical formula naphthalene → C₅H₄

    Explanation:

    Centesimal composition means that in 100 g of compound we have x g of the element. Therefore in 100 g of naphthalene we have:

    93.7 g of C

    6.3 g of H

    Let's make a rule of three:

    In 100 g of naphthalene we have 93.7 g of C and 6.3 g of H

    In 128 g of naphthalene we would have:

    128. 93.7 / 100 = 120 g of C

    128. 6.3 / 100 = 8 g of H

    We convert the mass to moles, by molar mass:

    120 g. 1mol / 12 g = 10 moles C

    8 g. 1mol / 1g = 8 moles H

    Molecular formula naphthalene → C₁₀H₈

    Empirical formula naphthalene → C₅H₄

    (The sub-index of each element is divided by the largest possible number)
Know the Answer?
Not Sure About the Answer?
Find an answer to your question 👍 “Naphthalene, commonly found in moth balls, is composed of 93.7% carbon and 6.3% hydrogen. The molar mass of naphthalene is 128 g/mol. ...” in 📗 Chemistry if the answers seem to be not correct or there’s no answer. Try a smart search to find answers to similar questions.
Search for Other Answers