General Chemistry Study Notes

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Questions and Answers

What is the empirical formula derived from the ratio of carbon, hydrogen, and oxygen given in the content?

C2H6O2
C3H8O
C5H11O2
CH3O (correct)

If a compound has a molar mass of 114 g/mol, what is the correct calculation of the percentage of oxygen in C5H11O2?

31.07%
38.46%
18.42%
28.95% (correct)

Which statement accurately describes how to determine the simplest ratio for a given compound?

Multiply all subscripts by the molar mass to obtain whole numbers.
Calculate the compound's total mass and divide by the number of atoms.
Determine the ratio of elements in moles and simplify to the smallest whole number. (correct)
Divide the atomic mass of hydrogen by the total mass of the compound.

What is the crucial first step in finding the percentage composition of an element in a compound?

Calculate the total molar mass of the compound. (C) Signup and view all the answers

What is the relationship between the empirical formula and the molecular formula?

The molecular formula is a multiple of the empirical formula. (D) Signup and view all the answers

When calculating the molar mass of oxygen for C5H11O2, what value should be used for oxygen's atomic mass?

16.00 g/mol (C) Signup and view all the answers

If the ratio of moles for hydrogen in a compound is approximately 4, what does this indicate about the number of hydrogen atoms?

There are 4 hydrogen atoms. (A) Signup and view all the answers

What should you do if the ratio of an element in a compound results in a fractional value?

Multiply all subscripts by the denominator of the fraction. (A) Signup and view all the answers

What is the empirical formula derived from the moles of carbon, hydrogen, and oxygen calculated from the percentages provided?

C₃H₈O (C) Signup and view all the answers

How many moles of oxygen are contained in a 100g sample of the compound described?

3.75 mol (C) Signup and view all the answers

If the molar mass of the compound is 180 g/mol and the empirical formula mass is 60.07 g/mol, what is the factor used to determine the molecular formula?

3 (C) Signup and view all the answers

What is the molecular formula resulting from the empirical formula C₃H₈O using the determined factor?

C₉H₂₄O₃ (B) Signup and view all the answers

When finding the simplest ratio for the compound using moles of each element, what should be done first?

Divide each mole value by the smallest mole number. (B) Signup and view all the answers

What is the percentage composition of hydrogen in the compound if it contains 10% hydrogen by weight?

10% (B) Signup and view all the answers

What is the empirical formula mass of C₃H₈O calculated from its components?

60.07 g/mol (D) Signup and view all the answers

Which of the following formulas represents a possible molecular formula for the compound if the empirical formula is C₃H₈O?

C₉H₂₄O₃ (C) Signup and view all the answers

What is the percentage of hydrogen in water?

11.21% (D) Signup and view all the answers

What is the molar mass of carbon dioxide (CO₂)?

44 g/mol (A) Signup and view all the answers

Which compound has the highest percentage of oxygen?

Glucose (A) Signup and view all the answers

What is the simplest ratio of carbon to hydrogen in a compound containing 60% carbon and 13.33% hydrogen?

4:3 (D) Signup and view all the answers

Given its molar mass of 180 g/mol, what could be the molecular formula for a compound with empirical formula C₁₃H₁₆O₃?

C₁₃H₁₆O₃ (C) Signup and view all the answers

If a compound has a mass percentage composition of 26.67% oxygen, what mass of this compound corresponds to 100 g of sample?

26.67 g (B) Signup and view all the answers

Which of the following represents the correct calculation for determining the percentage of oxygen in ethanol (C₂H₅OH)?

(1 x 16.00 g/mol) / 46.07 g/mol x 100% (B) Signup and view all the answers

To calculate the empirical formula from mass percentages, which step is NOT necessary?

Determine the percentage composition (C) Signup and view all the answers

Flashcards

Empirical Formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

The actual number of atoms of each element in a molecule of a compound.

Molar Mass

The mass of one mole of a substance, measured in grams per mole (g/mol).

Finding Empirical Formula

Calculate moles of each element from percentage composition or mass, divide by the lowest mole amount to get simple ratio.