reaction rates

• Measuring rates of reaction

  Measuring the amount of product formed in a certain period of time
• The rate of reaction measures how much product is made in a given time
• Volume

  The volume of a three-dimensional shape is a measure of the amount of space or capacity it occupies
• The units for rate of reaction are commonly written as g/s, g/min, cm3/s, or cm3/min
• Units for rate of reaction

  • g/s
  • g/min
  • cm3/s
  • cm3/min
• Mass

  The amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g)
• The time period chosen for measuring the rate of reaction may vary depending on the speed of the reaction
• For reactions to occur, reactant particles must collide
• Chemical reactions vary in speed
• Methods of measuring rate of reaction

  1. Measuring the volume of gas given off by a reaction over time

  2. Measuring the loss of mass of a reaction over time when a gas is produced

  3. Measuring the amount of light that passes through a reaction mixture (as a precipitate forms) over time
• Measuring rates of reaction

  • Measuring the rate where a gas is produced
  • Measuring the rate where a precipitate forms
  • Calculating and comparing rates
• Advantages for gas syringe

  • Precise scale
  • No time delay in connecting the syringe
  • All the gas produced is from the reaction mixture
• The rate of reaction measures how much product is made in a given time
• Advantages for gas jar

  • No time delay in connecting the syringe
  • All the gas produced is from the reaction mixture
• For reactions to occur, reactant particles must collide
• Disadvantages for gas syringe

  • Gas jar does not have a precise scale
  • Tube beneath the trough may slip away from under the gas jar
• Measuring the rate where a gas is produced

  1. The apparatus needed depends on the nature of the product being measured

  2. Mass of a substance is measured with a balance

  3. Cotton wool is used in the neck of the flask to allow the gas to escape

  4. Volume of a gas is usually measured with a gas syringe when the chemical reaction produces a gas
• Disadvantages for gas jar

  • Precise scale
  • No time delay in connecting the syringe
  • All the gas produced is from the reaction mixture
• Chemical reactions vary in speed
• Factors affecting reaction rates include temperature, pressure (for gases), surface area, catalysts, and concentration.