College Chemistry

Lab Review for Final Exam

Experiment #1: Density

Density = Mass/VolumeVolume = length x width x heightUnits = g/mL or g/cc or g/cm3

Density Column

Practice Problem525 mL of water at 250C (density = 0.997 g/mL) is placed in a container. The water is then cooled to form ice at -100C (density = 0.917 g/mL).

What is the mass and volume of the ice?

Answer

Mass = 523 gramsVolume = 571 mL

Experiment #2: Safety, General Equipment & TechniquesSafety equipmentSafety TechniquesLaboratory equipmentGlasswareSeparation Techniques

Safety Shower

Practice Problem

What is a buret used for?

Answer

• For use with acid-base titrations• To deliver the solution of known

concentration in a titration

Experiment #3: Physical MeasurementsVolume = length x width x heightDisplacement MethodDensity = mass/volumeRelative UncertaintyAbsolute Uncertainty

Practice Problem

How do you determine relative uncertainty?

AnswerRelative Uncertainty is the ratio of the absolute

uncertainty of a measurement to the best estimate.

It expresses the relative size of the uncertainty of a measurement (its precision).

For example, The measurement 25.4 + 0.1 cm

Experiment #4: Composition of a Heterogeneous MixtureFiltrationDistillationDecantingChromatographyElectrolysis% Composition

Practice Problem

How can a heterogeneous mixture be separated?

Answer

•Heating•Filtration

Experiment #5: Isotopes & Atomic MassAtomic mass unit (amu)Weighted average of

atomic mass from %Different molecule

possibilities of isotopes

Practice Problem

Define an atomic mass unit (amu)

Answer

1/12 the mass of 1 Carbon – 12 atom

Experiment #6: Empirical Formula of a CompoundEmpirical formulaMolecular formulaStructural formulaWhy add water after

heating magnesium ribbon?Calculate empirical

formula from mass Caffeine

Practice Problem

What is the empirical formula of magnesium

oxide?

Answer

MgO

Experiments #7 & #8: Quantitative Analysis of HydratesHydrateCalculate unknown value of a hydrateCalculate mass of water produced in a

hydrateCalculate number of moles of water in a

hydrate Methane hydrateWhen organic material decomposes it

releases methane, also known as swamp gas. Combine water and swamp

gas under low temperatures and high pressures and the result can be a frozen lattice-like substance called methane hydrate. This crystalline

combination of a natural gas and water looks remarkably like ice but burns if lit

with a flame.

Practice Problem

If 16.4 grams of oxygen gas react with excess hydrogen,

what mass of water is produced?

Answer

Mass = 18.5 grams

Experiment #9: Concentration of acetic acid in vinegarTitration definition & formulaEnd pointCalculate molarityCalculate concentration

of unknown solution

Practice ProblemIf 25.00 mL of 0.200 M acetic acid is transferred into a volumetric flask and diluted to 5.00 x 10 2 mL,

What is the concentration of the resulting solution?

Answer

Concentration = 1.00 x 10 -2 M

Experiment #10: Material value of a metalIonic BondCovalent BondMetallic BondConductivityElectroplatingElectrolysisElectronegativity

Floating magnet

Practice ProblemWhen the pennies were heated in the NaOH solution, a layer of zinc bonded to the copper penny.

What type of bond would exist between the atoms of copper and zinc?

Answer

Metallic

Experiment #11:Molecular GeometryLewis StructuresLone pairsMolecular geometry chart (review)

Hybridization

Practice Problem

How many lone pairs are on a sulfur atom in the sulfite ion, SO3 2-?

Answer

1 lone pair

Experiments #12 & #13: Thermochemistry & Hess’ LawThermochemistryCoffee & Milk solution – heat of solutionq = mc ΔTEnthalpyHess’ Law

combustion

Practice Problem

Gold has a specific heat of 0.129 J/g0C. When a 5.00-g piece of gold absorbs 1.33J of heat, what is the change in temperature?

Answer

Temperature change = 2.06 0C