5 Steps to a 5 AP Chemistry

288  Step 4. Review the Knowledge You Need to Score High

Equipment

analytical balance buret clamp

desiccator drying oven Erlenmeyer flask

pH meter pipet support stand

wash bottle volumetric flask

Measurements

1.the volume of a solution of an oxidant or reductant using a pipet

2.the initial reading of the buret

3.the final reading of the buret at the endpoint of the titration

Calculations

The volume of titrant added is calculated by the difference between measurements

2 and 3.

The volume of titrant is then converted to liters.

The pipeted volume is converted to moles by multiplying the liters of solution by its

molarity. The moles of titrant are determined from the mole ratio in the balanced chemi-

cal equation for the reaction. The molarity of the solution is calculated by dividing the

moles of titrant by the liters of titrant used.

Comments

Common oxidants are potassium permanganate and potassium dichromate.

Iron(II) and oxalates are commonly chosen as reductants.

Refer to Figure 19.3 for general titration set-up.

Experiment 9: Mass/Mole Relationships in a

Chemical Reaction

Synopsis

The initial masses of various reactants may be determined and then converted to moles.

A similar calculation may be done for the products. (See the Stoichiometry chapter.)

Equipment

analytical balance beaker(s) desiccator

Erlenmeyer flask graduated cylinder hot plate

Measurements

1. mass of samples of different reactants


2. mass of samples of different products

Calculations

Convert the masses of the reactants and products to moles using their molar masses.

Using the mole ratios from the balanced chemical equation, it is possible to determine how

much material should react or be produced. These calculated values can be compared to the

observed values.

Comments

Nearly any reaction may be used.