DF 1

• Molar gas volume

  Volume a mole of gas occupies measured in decimeters cubed per mole
• Gases occupy the same volume of space under the same conditions
• Mole or gas calculations

  Number of moles = Volume (in decimeter cubed) / Molar gas volume
• The video is a revision video for OCR piece alters presented by Chris Harris from alarrytutors.com
• At standard room temperature and pressure, 1 mole of any gas occupies 24 decimeters cubed per mole
• The ideal gas equation can take into account differing temperatures and pressures
• Ideal gas equation

  PV = NRT
• Volume of a gas can be found experimentally by collecting it through a gas syringe or using an upturned measuring cylinder in a tank of water
• Gas volumes calculation using molar and volume calculations

  Moles = Mass / Relative atomic mass
• Unit conversion from meters to decimeters, decimeters to centimeters

  Multiply by 10 for each conversion
• Converting pressure from kPa to Pa

  Multiply by 1000
• When using the ideal gas equation, ensure to use the units provided and be able to rearrange the equation
• Unit conversion from meters² to centimeters²

  Multiply by 10,000
• Calculating volume of a gas using ideal gas equation

  Given values: N = 0.36 moles, R = 8.31, T = 298K, P = 100 kPa
• Converting volume from m³ to cm³

  Multiply by 1,000,000
• Gas constant R is 8.31, standard conditions are 298K and 101.3 kPa
• Unit conversion from meters³ to centimeters³

  Multiply by 1,000
• For meters³ to centimeters³ conversion, multiplying by a million is required for each additional dimension
• When converting volumes in chemistry, add an extra zero for each additional dimension
• For meters³ to centimeters³ conversion, multiply by 1,000 for each dimension
• Calculating volume of gas produced in a reaction

  Given values: 12g of potassium, 100 kPa pressure, 298K temperature, gas constant 8.31 J/(K*mol)
• Calculating moles of hydrogen produced

  Using stoichiometry from balanced equation
• Calculating moles of potassium

  Number of moles = mass / atomic mass
• Using ideal gas equation to calculate volume of gas

  Volume = (0.1115 * 8.31 * 298) / 100,000
• Volumes of gases produced in reactions can be measured using a gas syringe
• Measuring the volume of a gas

  Volumes of gases produced in a reaction can be measured using a gas syringe
• Standard state

  The substance is under standard conditions of 100 kilopascals and 298 Kelvin (25 degrees Celsius)
• For reactions producing a larger volume of gas in a short space of time, precautions need to be taken to prevent accidents
• Gas syringe measures the amount of gas produced in a reaction
• When the plunger doesn't move any further, the reaction has stopped and that volume can be measured
• Reactions can either give out heat energy (exothermic) or absorb heat energy (endothermic)
• Enthalpy change (ΔH)

  The heat change in a reaction at a constant pressure, symbolized by ΔH in kilojoules per mole
• Enthalpy change is a change in energy during a chemical reaction
• Preliminary experiments may be needed to adjust reactants or equipment if the gas produced is more than expected
• Endothermic reactions absorb energy from the surroundings, while exothermic reactions release energy to the surroundings
• Bond breaking is an endothermic process as energy is absorbed when bonds are broken
• Bond making is an exothermic process as energy is released when bonds are formed
• If more energy is released when bonds are formed than needed to break them, the overall reaction is exothermic
• Bond enthalpy is the amount of energy needed to break one mole of a bond type in a molecule in the gaseous state
• Bond enthalpy

  The amount of energy needed to break one mole of a bond type in a molecule in the gaseous state