Chemistry Lab Final 3 Flashcards

Compound Formulas

• Simplest formula: lowest whole number ratio of atoms in a compound.

Hydrates and Anhydrates

• Hydrate: ionic compound combined with a specific number of water molecules.
• Anhydrate: removes water, leaving a pure ionic compound.

Heating Hydrates

• Heating causes water in hydrates to evaporate, resulting in the removal of water molecules.

Mass Loss Calculations

• To find mass of water lost from a hydrate, subtract anhydrate mass from hydrate mass.
• Example: 6.00g hydrate - 3.27g anhydrate = 2.73g H2O lost.

Percentage of Water in Hydrate

• Calculate % water in hydrate using: (mass of H2O / mass of hydrate) x 100.
• Example: (2.73g / 6.00g) x 100 = 45%.

Chemical Equations

• Dehydration of CoCl2 hydrate:
  • 6H2O + CoCl2 -(HEAT)-> CoCl2 + 6H2O.
• Balanced equation for Mg with O2:
  • 2Mg + O2 -(HEAT)-> 2MgO.
• Dehydration of MgSO4 hydrate:
  • MgSO4 + 7H2O -(HEAT)-> MgSO4 + 7H2O.

Osmosis and Cell Membranes

• Cucumber in concentrated salt solution: placement in hypertonic solution draws water out via osmosis.
• Semipermeable cell membranes allow nutrient intake.

Mixtures and Solutions

• Solutions can be filtered out by semipermeable membranes.
• Colloids consist of smaller particles that cannot be filtered by filter paper.
• Suspensions contain larger particles also unable to be filtered by paper.

Concentration Differences

• Higher concentration solutions yield greater osmotic effects; examples include various concentrations of starch and glucose.

Effects of Solutions on Cells

• Hypertonic solutions cause crenation; hypotonic solutions lead to hemolysis.
• Isotonic solutions exhibit no change in cell shape.

Indicators and Reactions

• Benedict's reagent turns orange-red for glucose; iodine turns blue-black for starch; AgNO3 forms white precipitate with chloride.
• Dialysis bag experiments reveal molecules like glucose and Cl- crossing semipermeable membrane.

Gas Laws and Pressure

• Combined gas law: P1V1/T1 = P2V2/T2; rearranged gives V2 = V1P1T2/P2T1.
• Distinction between vapor pressure (pressure of vapor over liquid) and atmospheric pressure (force exerted by atmosphere).

Standard Conditions

• Standard temperature and pressure (STP): 0°C (273K) and 1 atm (760 mmHg).
• Molar volume of a gas at STP is 22.4 L/mol.

pH and Solutions

• pH is closely related to [H3O+]: pH = -log[H3O+].
• Adding an acid to water raises [H+] and lowers pH; adding a base raises the pH.

Buffer Systems

• Buffers stabilize pH by neutralizing excess acids or bases—maintaining equilibrium.
• Blood pH between 7.35 and 7.45 managed by bicarbonate buffer system.

Neutralization Reactions

• Neutralization involves H+ ions from an acid and OH- from a base forming salt and water.
• Example reaction: H2SO4 + 2 KOH → K2SO4 + 2 H2O.

Titration Process

• Titration determines the amount of base needed to neutralize an acid using indicators for endpoint detection.