CHEM121L Final Definitions & Equipment

Accuracy

how close a measurement is to the true value

Precision

a measure of how close a series of measurements are to one another

Limiting reactant

A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product.

Metathesis reaction

Cations and ions of the reaction change partners

AC + BD -> AB + CD

Combination reaction

A chemical change in which two or more substances react to form a single new substance

A + B -> AB

Decomposition reaction

A reaction in which a single compound breaks down to form two or more simpler substances

AD -> AB + C

Single displacement

One element trades places with another element in a compound

AC + B -> A + BC

Oxidation reduction reaction

Any chemical change in which one species is oxidized (loses electrons) and another species is reduced (gains electrons); also called redox reaction

A -> A^n+ + ne^- (Decomp)

B + me^- -> Bm^- (Reduct)

Mixture

A combination of two or more substances that are not chemically combined

Pure substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

Chemical property

A characteristic of a pure substance that describes its ability to change into different substances

- Reactivity, flammability, toxicity

Physical property

A characteristic of a pure substance that can be observed without changing it into another substance

- Boiling point, melting point, solubility, density

Homogenous mixture

A mixture in which the composition is uniform throughout

Heterogenous mixture

A mixture with uneven distribution of different substances, solids, liquids, and gases.

Extraction

The process used to isolate or purify a substance. This process selectively removes a compound of interest from a mixture based on its solubility in a particular solvent.

Filtration

The separation of a liquid from a solid particle size through a porous medium, such as filter paper.

Decantation

The separation of a liquid from a solid by pouring. The solid is allowed to settle to the bottom of its container, and the supernatant liquid is poured off, leaving the solid behind in the original container.

Evaporation

The process used to separate a solvent from a solution by heating. The solvent is driven from the solution, leaving behind the previously dissolved residue.

Handle hot objects with

Tongs

As the volume of the heated solution decreases, the risk of splattering increases. How do you prevent this?

Gentle heating and attentiveness

HCL is dangerous because

It is a corrosive, toxic substance that can cause burns

Qualitative analysis

Part of analytical chemistry that determines what compounds are present

Quantitative analysis

How much of the compound is present

Analyte

Chemical compound of interest

Gravimetric determination

The analyte is precipitated as an insoluble compound and weighed

Volumetric determination

Amount of analyte is determined by measurements of solution volumes that react with the analyte

Standardization

Determining molar concentration (molarity)

Titration

The process of slowly adding one solution to another until the reaction between the two is complete

Acid-base indictator

A solution that changes color depending on the pH (acid content) of the solution

The color of phenolphthalein (indicator)

Colorless in acidic and neutral solutions and pink in basic (alkaline) solutions

Titrant

Solution in the buret

End point

The indicator changes color, signaling that the reaction between the two is complete

Equivalence point

The analyte has completely reacted with the titrant

- Theoretical point that is calculated

What should you do if NaOH spills on your skin?

Immediately wash with water for 15 minutes (inform your TA after)

What should you do if NaOH spills on a surface?

Neutralize the surface with baking soda, rinse it with water, wipe it clean, and tell your TA

Polymer

Large molecule/macromolecule made up of repeating monomer units which are smaller chemical building blocks

Monomer

Molecule that bonds with other monomers to form large structures called polymers

What should you do if you get polyacrylate powder on your skin?

Rinse with water (avoid inhaling it)

Spectator ion

Ions that do not participate in a reaction

Intermolecular forces

Forces between molecules

VESPR theory

Used to predict the geometry of a molecule based on the Lewis structure

Scoopula

Used to transfer solids

Erlenmeyer flask

Used to hold liquids, has narrow neck to prevent splashes

Beaker

An open cylindrical container with a pouring lip; used for mixing larger amounts of substances

Pipet

Used for exact measurements of liquids

Buret

Dispensing and transferring known volumes of fluids

Graduated cylinder

Instrument used to measure volume of a liquid

Test tubes

Holds liquids for observation or testing

Rubber policeman

A hard tipped rubber scraper used to transfer precipitate

Evaporation dish

Used to hold liquids for evaporation. The wide mouth allows vapor to escape.

Ceramic plate

Holds hot apparatus

Electronegativity

Ability of an atom in a covalent bond to attract the shared electrons that bond

Bunsen burner

A common laboratory device used for heating, sterilization, and combustion. It produces a single open gas flame, which can be adjusted for intensity and size. Bunsen burners are typically fueled by natural gas or propane, allowing for efficient and controlled heating in experiments.