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1

Weighing Errors

  1. samples must be at ambient temperature to prevent errors due to convective air currents.
  2. Warmth of hands/fingertips can affect the apparent mass of an object.

2

Buoyancy

The upward force exerted on an object in a liquid or gaseous fluid. 

An object weighed in the air appears lighter than its actual mass by an amount equal to the mass of air that the object displaces.

3

Ordinate

y-axis of a graph

4

Abscissa

X-axis of a graph

5

Solute

Minor species in a solution.

6

Solvent

Major species in a solution

7

Concentration

States how much solute is contained in a given volume or mass of solution or solvent.

8

Mole (mol)

Avogadro's number of particles (atoms, molecules, ions, etc).

9

Molarity (M)

The number of moles of a substance per liters of solution.

10

Atomic Mass

The number of grams containing Avogadro's number of atoms.

11

Molecular Mass

The sum of atomic masses of the atoms in the molecule.

12

Electrolyte

A substance that dissociates into ions in solution.

13

Formal Concentration (F)

The molarity of a strong electrolyte.

14

Formula Mass

The molecular mass of a strong electrolyte.

15

Molality (m)

Concentration expressed as moles of substance per kilogram of solvent (not total solution).

16

Gravimetric Analysis

Chemical analysis based on weighing a final product.

17

Stoichiometry

The calculation of quantities of substances involved in a chemical reaction.

18

Volumetric Analysis

Procedures in which the volume of reagent needed to react with analyte are measured.

19

Analyte

Substance being measured.

20

Titration

A form of volumetric analysis in which increments of reagent solution - the titrant - are added to analyte until their reaction is complete.

21

22

Equivalence Point

Occurs when the quantity of added titrant is the exact amount necessary for stoichiometric reaction with the analyte.

23

End Point

Marked by a sudden change in physical property of the solution.

24

Indicator

A compound with a physical property (usually color) that changes abruptly near the equivalence point.

Change is caused by disappearance of analyte or appearance of excess titrant.

25

Blank Titration

A method of estimating titration error by which we carry out the same procedure without analyte.

26

Direct Titration

Titrant is added to analyte until the reaction is complete.

27

Back Titration

Add a known excess of one standard reagent to the analyte.

Usefule when its end point is clearer than the end point of the direct titration.

28

Gravimetric Titration

Titrant is measured by mass, not volume.