Chem - Quantitative chemistry

• What does the law of conservation of mass state?

  No matter is lost or gained during a chemical reaction.
• what is a precipitate?

  an insoluble solid
• Why might the mass of a reaction flask be found to increase?

  One of the reactants is a gas found in the air and all of the products are either solids or liquids.
• What is an error?

  The difference between a value or quantity obtained in an experiment.
• What are the 2 types of error?

  random error and systematic error
• How can random error be affected?

  - The person reading the scale poorly

  - Change in environment, for example, a change in temperature
• What is systematic errors?

  Errors that occur as a result of a faulty or poorly designed experimental procedure.
• What is the value of the Avogadro constant?

  6.02 x 10^23 per mole

  
• what is a molar mass?


  When one mole of any element is equal to the relative atomic mass of the element in grams.
• What is the equation for moles?

  Moles = mass ÷ Mr

  
• What is meant by concentration?

  The amount of solute there is in a specific volume of the solvent.
• What is the equation for concentration?

  Concentration = mass ÷ volume

  
• What is yield?

  A term used to describe the amount of product you get from a reaction.
• Why will you never get 100% of yield in a chemical process?

  - some reactants may be left behind in the equipment

  - the reaction may be reversible and a high yield is never possible as the products are continually turning back into the reactants

  - some products are lost during separation and purification stages, such as filtration or distillation.

  - product lost when transferring from one container to another.
• What is actual yield?


  The recorded amount of product obtained
• What is theoretical yield?

  The amount of product that would be obtained under perfect practical and chemical conditions
• How to calculate percentage yield?

  percentage yield = actual yield÷theoretical yield x 100

  
• What is atom economy used for?

  To analyse the efficiency of reactions
• How do you calculate atom economy?

  Atom Economy = Total Mr of the desired product ÷ Total Mr of all the products × 100

  
• What factor needs to be considered when choosing a reaction pathway?

  - Atom economy

  - Percentage yield

  - Rate of reaction

  - Equilibrium position
• What is a reaction pathway?

  The sequence of reactions needed to produce a desired product from a particular set of raw materials.
• How do you calculate concentration in mol/dm3?

  Moles ÷ Volume

  
• How do you go from g dm-3 to mol dm-3?

  Divide by the Molar mass in grams and vice versa.
• What does Avogadro's Law state?

  At the same condition of temperature and pressure, an equal amount of gasses occupy the same volume of space.
• What does the molar gas volume at RTP mean?

  The volume occupied by 1 mol of any gas was found to be 24dm^3 or 24,000cm^3.
• What does RTP stand for?

  Room temperature and pressure
• How do you calculate volume?

  Volume = Mass × Molar Volume