CHEM LAB FINAL (!!!!!!)

Freezing Point Depression

drop in at the highest temperature at which a substance freezes, happens when a smaller amount of non-volatile substance is added.

Freezing Point Depression

ΔT = Kf * m, the ΔT is the change in freezing point, the Kf is the molal freezing point depression constant, and m is the molality of the solution.

Freezing Point of a Solution given Solute and Solvent Mass

Adding the solute to the solvent will decrease the freezing point of the solvent. The solute is dissolved when the solvent is proportional to the molal concentration, m, of the solute is present.

Molar Mass

Multiply the atomic weight of each element by the number of atoms of that element present in the compound.

Primary Standard

The reagent can be weighed easily, it is pure that the weight truly represents the number of moles of substance contained.

Secondary Standard

Has less purity, is less stable and is more reactive, the reaction remains stable for a long time.

Five Requirements of Primary Standard

High Purity, low reactivity, low weight change due to humidity, High weight to minimize weighing errors, concentration remains unchanged for long periods of time, and non-toxic.

Why must CO2 be removed for NaOH and HCI to be standardized?

The base reacts with carbon dioxide to yield the hydrogen carbonate and carbonate. We use the water from all carbon dioxide that has been removed to prepare any sodium hydroxide solution for it to be standardized.

EX: 2 Is Phenolphthalein an appropriate indicator?

The pH would be around 8-9 and the color change is basic color and if acidic it is colorless.

calculating concentration from titration data

M AV A = M BV B Let's assume you are titrating a strong acid (10 mL unknown concentration HCl) with a strong base (1.0 M NaOH). It takes 25mL of NaOH to neutralize the acid.

Heterogenous mixtures complications

A mixture that is not uniform in composition and does not blend smoothly.

Suspensions

heterogenous mixture in solid particles does not dissolve, it does get suspended throughout the solvent, left floating around freely in the medium.

Colloids

heterogeneous mixtures in which particles of an insoluble substance are suspended throughout another substance.

Strong acid-base titration

the curve begins acidic and turns basic after the equivalence point, which occurs at the pH=7.

Indicator in experiment #3?

phenolphthalein

Changes in pH cause change in the color of indicator.

compounds that change color when they become protonated or deprotonated. Because this color change occurs over a specific pH range, indicators can be used to approximate the equivalence point of an acid–base titration.

solubility equilibria

when the dissolution and precipitation of a solute species occur at equal rates.

solubility equilibria (temperature)

An increase in temperature puts stress on the equilibrium condition and causes it to shift to the right. The stress is relieved because the dissolving process consumes some of the heat. Therefore, the solubility (concentration) increases with an increase in temperature.

Complex Ion Equilibria

Complex ions typically exist in complex equilibrium involving its central metal ion and the ligands. A metal ion in solution does not exist in isolation, but in combination with ligands (such as solvent molecules or simple ions) or chelating groups, giving rise to complex ions or coordination compounds.

Dissolving Insoluble Solids

For ionic compounds containing basic anions, solubility is inversely proportional to pH solubility increases as the pH of the solution decreases. In many sparingly soluble salts, the anion is the conjugate base of a weak acid.

Bronsted-Lowry acid

any species that is capable of donating a proton. A Brønsted-Lowry base is any species that is capable of accepting a proton, which requires a lone pair of electrons to bond to the ‍ . Water is amphoteric, which means it can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base.

Bronsted-Lowry base

The Brønsted-Lowry theory describes acid-base interactions in terms of proton transfer between chemical species. A Brønsted-Lowry acid is any species that can donate a proton, and a base is any species that can accept a proton.

How does buffering work in chemistry?

A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.

calculating % dissociation

The percentage of dissociation of a compound will vary depending on the solvent. To calculate the percentage of dissociation of a compound, divide the mass of the dissociated ions by the total mass of the dissociated and not dissociated compound, then multiply by 100.

What is a ICE table ?

An ICE (Initial, Change, Equilibrium) table is simple matrix formalism that used to simplify the calculations in reversible equilibrium reactions (e.g., weak acids and weak bases or complex ion formation).

mass action expression

equation that shows the ratio of the product activities raised to the power of their coefficients to that of the reactant activities raised to the power of their coefficients.

what are antacids used for and how do they work?

Antacids help to treat heartburn (indigestion). They work by neutralizing the stomach acid that causes heartburn. You can buy many antacids without a prescription. Liquid forms work faster, but you may prefer tablets because they are easy to use.

rate-determining step

Rate determining step is the slowest step within a chemical reaction. The slowest step determines the rate of chemical reaction.

order of reaction

the power dependence of rate on the concentration of all reactants.

Oxidation

a process that occurs when atoms or groups of atoms lose electrons.

Reduction

the process of an atom or compound gaining one or more electrons.

Voltaic Cell

an electrochemical cell that uses a chemical reaction to produce electrical energy. The important parts of a voltaic cell: The anode is an electrode where oxidation occurs. The cathode is an electrode where reduction occurs.