CHM 113 Lab Final

Intensive Property

independent of size of sample (density)

Extensive Property

depend on size of sample (volume and mass)

Levitating

hovering in middle of solution (same densities)

specific gravity

ratio of density of the substance to density of water

equivalent weight

the weight of the substance which will react with or produce one mol hydrogen

Total pressure of gas inside buret

𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑃𝑤𝑎𝑡𝑒𝑟 𝑣𝑎𝑝𝑜𝑟 + 𝑃𝑤𝑎𝑡𝑒𝑟 + 𝑃𝑑𝑟𝑦 𝑔𝑎s

Requirements for gravimetric analysis

compound must be pure/known stoich, percent yield >99.9%, minimal interference of precipitates forming by other compounds, large crystal precipitates, high weight of precipitate generated

Flocculation

aggregate into a mass, so precipitate dissolves first and re-precipitates to create larger particle

Calculate Ba(OH)2 from titration

equiv. pt -> find moles from molarity -> use moles to find concentration

Calculate Ba(OH)2 from crucible

mass of precipitate x mol/molar mass -> mol/L

state function

depend only on the intial and finals states of the system and not on the path taken

Hess's Law

if a reaction is carried out in a series of steps, change H for the reaction will equal the sum of the enthalpy changes for individual steps

enthalpy of formation (change H)

heat given off when one mole of a substance is prepared for its constituent elements in their standard states, units is kJ/mol or J/mol

Beer's Law

𝐴 = 𝜀C (a absorbance, e molar absorptivity, c concentration)

Why spectrophotometer?

measures quantitively how much light of a specific wavelength passes through a solution, used because concentrations so low

Why hydroxylamine?

to reduce Fe3+ to Fe2+

Why ammonium acetate?

Buffer because hydroxylamine pushes reaction to the right

ppm

parts per million bases, mg/L

Ksp

solubility product constant, increase = more soluble
equation= [A]^n [B]^n

Why add NH3?

when added to Cu2+, creates dark blue color, strong interactions

Why no Beer's Law for Ksp Lab?

Calibration curve is not straight line, so calibration curve must be used

Ka expression

𝐾𝑎 =[𝐻3𝑂+][𝐴−]
[𝐻𝐴]

Henderson Hasselbach

𝑝𝐻 = 𝑝𝐾𝑎 + log [𝐴−]
[𝐻𝐴]

When titration @ half equiv point

[A-] = [HA] : pKa = pH

How is carbonate CO3 ^2- converted to carbonic acid H2CO3

back titration, add known excess of acid and react completely, brief boil to remove CO2, back titration with base

Freezing point when impurities present

lowered, needs cooling to lower temperatures compared to pure solvent

colligative property

property that only depends on the amount of solute present in solution, not identity of solute

molality

moles solute/moles solvent

molarity

moles solute/volume of solution

freezing point depression expression

∆𝑇 = 𝐾𝑓 ∙ m