Multiple Choice
Which of the following shows the correct number of atoms of each element in the formula Mg(NO3)2?
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3. Chemical Reactions
Empirical Formula
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Given that the empirical formula of a compound is C_3H_5 and its molecular mass is 205.4 g/mol, what is the value of n in the relationship: molecular formula = (empirical formula)_n?
A
n = 4
B
n = 3
C
n = 2
D
n = 1
Verified step by step guidance1
Calculate the molar mass of the empirical formula C_3H_5 by summing the atomic masses of its atoms: use 12.01 g/mol for carbon and 1.008 g/mol for hydrogen. The formula is \(\text{Molar mass}_{empirical} = 3 \times 12.01 + 5 \times 1.008\).
Determine the value of \(n\) by dividing the given molecular mass by the molar mass of the empirical formula: \(n = \frac{\text{Molecular mass}}{\text{Molar mass}_{empirical}}\).
Interpret the value of \(n\) as the number of empirical formula units in the molecular formula, which means the molecular formula is \((C_3H_5)_n\).
Verify that \(n\) is an integer or very close to an integer, since molecular formulas are whole number multiples of empirical formulas.
Use the value of \(n\) to write the molecular formula by multiplying the subscripts in the empirical formula by \(n\).
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