3.1.2.5 Balanced equations and associated calculations.

• What is the equation for percentage atom economy?

  % atom economy = molecular mass of desired products / total molecular mass of reactants x 100 (for percentage)
• What is the equation for a yield of a reaction?

  % Yield = Mass of product obtained / Theoretical mass of product x 100 (to get percentage)
• What is the indicator used for alkali in titrations and what is the colour change from alakali to neutral?

  Indicator = Phenolpthalein

  Colour change = Pink to colourless
• What is the indicator used for acids and what is the colour change from acidic to neutral?

  Indicator = Methyl orange

  Colour change = Red to yellow
• What is the first stage of PREPARING a solution of known concentration? (Titre)

  -Place beaker on a balance and press tare. (This zeros the balance.)

  -Transfer known mass of solid into beaker.

  -Record the mass.
• What is the second stage of PREPARING a solution of known concentration? (Titre)

  -Add distilled water, LESS than 250cm^3 to the beaker.

  -Dissolve the solid in the water by stirring.
• What is the third stage of PREPARING a solution of known concentration? (Titre)

  -Transfer the solution to volumetric flask.

  -Wash the final contents of the beaker into the volumetric flask.

  -Add distilled water up to 250cm^3 mark using a pipette. (Bottom of the meniscus.)

  -Invert the volumetric flask to make sure the concentration is even throughout the flask.