Chemistry Problems

Many chemistry problems require conversions between different units for mass or weight, such as grams, kilograms, pounds, and ounces.

• Grams to Kilograms Mass Conversion Problem
• Grams to Kilograms - Example #2
• Kilograms to Grams
• Pounds to Kilograms Mass Conversion Problem
• Ounces to Grams Mass Conversion Problem

Mass percent composition or mass percentage is one way of representing the concentration of an element in a compound or a component in a mixture. Mass percent composition is calculated as the mass of a component divided by the total mass of the mixture, multiplied by 100%.

• Calculate Mass Percent Composition - Worked Problem #1
• Mass Percent Composition - Worked Problem #2

Find the molecular mass by adding up the atomic masses of all of the atoms in the molecule.

• Molecular Mass - Worked Problem #1
• Molecular Mass - Worked Problem #2

A mole is defined as the quantity of a substance that has the same number of particles as are found in 12.000 grams of carbon-12. This number, Avogadro's number, is 6.022x10²³. The mass in grams of one mole of a compound is equal to the molecular weight of the compound in atomic mass units. One mole of a compound contains 6.022x10²³ molecules of the compound. The mass of 1 mole of a compound is called its molar weight or molar mass.

• Determining Number of Moles in Balanced Equations
• Molar Mass Problem
• Gram to Mole Conversion
• Mole to Gram Conversion

The Nernst equation is used to calculate the voltage of an electrochemical cell or to find the concentration of one of the components of the cell.

• Nernst Equation Worked Problem

Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. The decomposition process is called radioactivity.

• Mass - Energy Relations in Nuclear Reactions
• Atomic Mass & Isotopic Abundance
• Atomic Mass from Atomic Abundance
• Carbon-14 Dating
• Rate of Radioactive Decay

There are several ways to define acids and bases, but pH only refers to hydrogen ion concentration and is only meaningful when applied to aqueous (water-based) solutions. A buffer is an aqueous solution that has a highly stable pH. Many chemistry problems deal with pH and buffers:

• Quick Review of pH Calculations
• Sample pH Calculation
• pH of a Strong Acid
• pH of a Weak Acid
• pH of a Strong Base
• pH of a Buffer Using the Henderson Hasselbalch Equation
• Neutralizing a Base with an Acid
• Prepare a Phosphate Buffer
• pOH Calculation

Pressure is a measure of the force applied over a unit area. Pressure often is expressed in units of pascals or pounds per square inch.

• Pressure Conversion - kPa to mm Hg
• Pressure Conversion - mm Hg to kPa
• atmospheres to Pascals
• Pascals to atmospheres
• bars to atmospheres
• millibars to atmospheres
• atmospheres to bars
• atmospheres to millibars
• millibars to mm Hg
• mm Hg to millibars
• mm Hg to millibars
• psi to Pascals
• psi to atm
• psi to millibars
• atm to psi

Learn how to calculate half-life and how to determine the products of nuclear decay reactions.

• Half Life
• Alpha Decay
• Electron Capture
• Beta Decay
• Beta Plus Decay
• Rate of Radioactive Decay
• Carbon-14 Dating Problem

Raoult's Law can be used to calculate the change in vapor pressure by adding a nonvolatile liquid to a solvent or when adding a strong electrolyte to a solvent.

• Raoult's Law - Example #1
• Raoult's Law - Example #2
• Raoult's Law - Example #3