Calculating Molecular Formula
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Questions and Answers

What is the purpose of an empirical formula?

  • To depict how atoms are bonded in a compound
  • To determine the molecular mass of a compound
  • To show the elements present in a compound (correct)
  • To calculate the number of atoms in a molecule

Which type of bond information is NOT provided by a structural formula?

  • Ionic bond (correct)
  • Double covalent bond
  • Single covalent bond
  • Triple covalent bond

How is the formula mass different from the molecular mass?

  • Formula mass shows the exact number of atoms, while molecular mass doesn't
  • Formula mass includes all types of bonds, while molecular mass only includes covalent bonds
  • Formula mass is the mass of one formula unit, while molecular mass is the mass of one molecule (correct)
  • Formula mass is for ionic compounds, while molecular mass is for covalent compounds

Which formula would be most helpful in determining the number of atoms in a molecule?

<p>Molecular formula (C)</p> Signup and view all the answers

If a compound has the empirical formula CH2O, what could be its molecular formula?

<p>C2H4O2 (C)</p> Signup and view all the answers

What is the empirical formula of the compound that contains 40.9% C, 4.58% H, and 54.51% O by mass?

<p>CH2O (B)</p> Signup and view all the answers

In the compound with 30.43% N and 69.57% O by mass, what is the molecular formula?

<p>N2O4 (C)</p> Signup and view all the answers

If a compound has a molecular weight of 180 g/mol and contains 40.0% C, 6.6% H, and 53.4% O, what is its molecular formula?

<p>C6H12O6 (D)</p> Signup and view all the answers

What is the empirical formula for a compound that consists of 49.5% C, 5.20% H, 28.8% N, and 16.5% O by mass?

<p>C3H5NO (D)</p> Signup and view all the answers

Determine the molecular formula for a compound with a molecular weight of 194.1 g/mol and an empirical formula of CH2O.

<p>(CH2O)2 (B)</p> Signup and view all the answers

A compound comprises 92 g/mol with 30.43% N and 69.57% O by mass. What is its empirical formula?

<p>NO2 (B)</p> Signup and view all the answers

What is the empirical formula defined as?

<p>The formula with the smallest possible whole numbers of elements (D)</p> Signup and view all the answers

How does the percent composition of a compound relate to its empirical formula?

<p>Percent composition leads to the determination of the empirical formula (A)</p> Signup and view all the answers

In the compound containing 25.93% nitrogen and 74.07% oxygen, what is the empirical formula?

<p>NO3 (D)</p> Signup and view all the answers

What does stoichiometry deal with in chemistry?

<p>Chemical reactions (D)</p> Signup and view all the answers

What information does the molecular formula provide about a compound?

<p>It shows the simplest ratio of atoms in a compound (B)</p> Signup and view all the answers

How are subscripts represented in an empirical formula?

<p>As integers (B)</p> Signup and view all the answers

Study Notes

Stoichiometry

  • Branch of chemistry that deals with quantitative laws of chemical combination
  • Concerned with measurements based on chemical combination

Empirical Formula

  • Simplest formula for a compound, defined as the ratio of subscripts of the smallest possible whole number of elements present
  • Also known as the simplest formula
  • Gives information about the ratio of numbers of atoms in a compound
  • Can be determined from percent composition of a compound

Examples of Empirical Formula

  • PtCl2N2H6 (Cisplatin) from 65.0% Pt, 23.6% Cl, 9.35% N, and 2.05% H by mass
  • NO3 from 25.93% N and 74.07% O
  • C4H5N2O from 49.5% C, 5.20% H, 28.8% N, and 16.5% O by mass
  • CH2O from 40.0% C, 6.6% H, and 53.4% O by mass
  • NO2 from 30.43% N and 69.57% O

Molecular Formula

  • Formula that shows the actual number of atoms of each element in a compound
  • Can be determined from empirical formula and molecular mass
  • Examples: C6H12O6 (Glucose), N2O4 (Dinitrogen tetroxide), C6H8O6 (Ascorbic acid or Vitamin C)

Structural Formula

  • Displays the atoms of the molecule in the order they are bonded
  • Shows how the atoms are bonded to one another (single, double, and triple covalent bonds)
  • Examples: C3H8 (Propane), C4H10 (Butane), CH4 (Methane), C2H6 (Ethane)

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Description

This quiz challenges your ability to determine the molecular formula of a compound based on given percentages and molecular mass. Calculate the empirical formula first before deriving the molecular formula.

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