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The empirical formula and the empirical formula molar mass of one compound is C3H7 and 43g/mol....

Question:

The empirical formula and the empirical formula molar mass of one compound is C3H7 and 43g/mol. If the molar mass of the compound is 172g/mol, the molecular formula of the compound is:

a. C6H14

b. C9H21

c. C12H28

d. C3H7

Based on the chemical formula of glucose (C6H12O6), select all the true statements.

a. In 1 mol of glucose there are 6 mols of carbon.

b. The element with higher mass percent in glucose is hydrogen.

c. In 1 molecule of glucose there are 6 atoms of carbon.

d. The mass percent of carbon and oxygen in glucose is the same.

How many moles of carbon are in 90g of glucose(C6H12O6)?

Assume that the molar mass of glucose is 180g/mol.

Empirical Formula and Molecular Formula:

The empirical formula of a substance represents the simplest ratio of elements present in the substance, whereas the molecular formula of the substance represents the exact number of atoms of each element present in the compound.

For example, a compound with the molecular formula {eq}A_{n}B_{2n}C_{3n} {/eq} has the empirical formula {eq}AB_{2}C_{3} {/eq}

Answer and Explanation:

The ratio of the molar mass of the substance to its empirical formula mass is:

{eq}=\dfrac{172g/mol}{43g/mol} {/eq}

{eq}=4 {/eq}

Thus, the empirical formula of the compound is to be multiplied by 4 to get its molecular formula.

Thus, the molecular formula of the compound is:

{eq}C_{3\times 4}H_{7\times 4} {/eq}

{eq}=C_{12}H_{28} {/eq}

Thus, option (c) is the correct answer.

_____

The chemical formula of glucose has 6 carbon atoms, thus 1 mol of glucose would have 6 moles of carbon.

Mass of carbon in glucose = 6 (Atomic mass of C) = 6(12) g = 72 g

Mass of hydrogen in glucose = 12 (Atomic mass of H) = 12 (1) = 12 g

Mass of oxygen in glucose = 6 (Atomic mass of O) = 6 (16) g/mol = 96 g

Thus, the element with the highest mass percent in glucose is O.

Thus, options (a) and (c) are correct.

_____

The number of moles (n), given mass (w) and molar mass (M) of a substance, are related as:

{eq}n=\dfrac{w}{M} {/eq}

Thus, the number of moles of glucose in the given sample is:

{eq}\Rightarrow n=\dfrac{90g}{180g/mol}=0.5mol {/eq}


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What is Molar Mass? - Definition, Formula & Examples

from General Studies Science: Help & Review

Chapter 27 / Lesson 24
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