Chemistry Final Review

What is formula mass/molecular mass? How do you calculate it? What are its units?

* the mass of an individual formula unit or molecule
* it is found by calculating the sum of the masses of atoms that make up a single molecule or formula unit
* the units are g/mol

What are moles? How do you find them?

* the amount of "things" that make something up
* mass of compound in grams/molar mass

mole conversions

1 mol of an element\=molar mass; 1 mol\=6.02*10^23 atoms/molecules/formula unti/ion

What is percent composition?

\-the percentage by mass of each element in a compound

\-amount of one component (100)/total amount of stuff

What is empirical formula? when does it represent the actual composition of a substance?

* a chemical formula showing the ratio of elements in a compound rather than the total number of atoms
* when the substances is made up of the smallest ratio of atoms it is able to be

What is the relationship between empirical formula and molecular formula?

* Molecular formulas tell you how many atoms of each element are in a compound
* empirical formulas tell you the simplest or most reduced ratio of elements in a compound
* If a compound's molecular formula cannot be reduced any more, then the empirical formula is the same as the molecular formula

What has to be true in a chemical reaction in relation to atoms, mass, and moles?

Conservation of atoms, mass, and moles must be observed in a chemical reaction.

What are the indicators that a chemical reaction has occured?

* light
* formation of precipitate
* gas evolved
* heat
* color change
* whole new substance

What is a precipitate? How does it form? From what type of reaction

* an insoluble solid formed by a reaction in solution
* new compounds that are formed in a chemical reaction are insoluble in water and precipitate out
* The are formed in special cases of double displacment reactions known as precipitation reactions

What are the diotomic molecules?

* hydrogen (H2)
* nitrogen (N2)
* oxygen (O2)
* fluorine (F2)
* chlorine (Cl2)
* bromine (Br2)
* iodine (I2)

What is done to balance a chemical equation?

* write each compond correctly
* place coefficients as needed in front of the symbols or formulas so the same number of each type of atom occurs in both reactants and products

What are the phase labels?

* solid (s)
* liquid (l)
* gas (g)
* dissolved in water (aq)

What are the types of chemical reactions?

* synthesis: puts chemicals together to make one product
* decomposition: takes chemicals and pulls them apart
* single replacement : B + AC = C + AB
* double replacement : EB + AC = EC + AB
* combustion: adding oxygen and resulting in a large amount of heat and light (always C, H, and O)

What does the mole to mole ratio come from? What is it used for?

* comes from the coefficients in a balanced chemical equation
* used as conversion factors between products and reactants

What is percent yield?

* actual yield/theoretical yield x 100
* percent yield is usually lower than 100% because the actual yield is often less than the theoretical value.

When does a gas undergo diffusion or effusion?

* gas undergoes diffusion when its particles move in an open area
* gas undergoes effusion when its particles move through a small opening

What changes the rate of diffusion or effusion?

* lighter masses / higher temps travel faster
* heavier masses / lower temps travel slower

What are indicators? How do they work?

* acid-base indicator is either a weak acid or weak base that exhibits a color change as the concentration of hydrogen (H+) or hydroxide (OH-) ions changes in an aqueous solution
* indicators are most often used in a titration to identify the endpoint of an acid-base reaction. They are also used to gauge pH values.

How do you know which indicator to choose?

* methyl red: pH- 4.2-6.3/Acidic/ red-yellow
* Bromothymol blue: pH- 6.0-7.6/Neutral/ yellow-blue
* Phenolphthalein pH- 8.2-10/Basic/ colorless-pink

What is an electrolyte? why do they matter?

* a solute that dissociates into ions that can conduct an electric current
* help keep the amount of water in your body balanced, as well as maintain pH levels and help move nutrients in and out of cells

What are some characteristics of acids?

\-sour

\-turns blue litmus paper red

\-can react with active metals to produce H2

\-reacts with bases to produce salts and water

\-conducts an electric current

\-warm toned colors on pH paper

What are some characteristics of bases?

\-Slippery feel

\-bitter taste

\-turns red litmus paper blue

\-reacts with acids to produce salts and water

\-conducts an electric current

\-cool toned colors on pH paper

What are the Arrhenius definitions of acids and bases?

* acids: produce H+ ions in aqueous solutions
* bases: produce OH- ions in aqueous solutions

What are the Bronsted-Lowery definitions of acids and bases?

* acids: substances that can donate a proton (H+) in aqueous solutions
* bases: substances that can accept a proton (H+) in aqueous solutions
* conjugate acid: the substance that is formed when the base accepts the proton (H+)
* conjugate bases: the substance that is left over after the acid has donated its proton (H+)

What are the strong acids?

* ionize completely in aqueous solutions
* HCl, HBr, HI, HNO3, H2SO4, HClO4
* weak conjugate bases

What are the strong bases?

* do NOT ionize completely in aqueous solutions
* LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
* weak conjugate acids

What are amphoteric substances?

* substances that can act as either an acid or a base
* OH-, H2O, H3O+
* SO4 2-, HSO4-, H2SO4-
* NH2 2-, NH3, NH4 +

How is a salt formed? What is it?

* a neutralization reaction in which an acid and a base react in an aqueous solution to produce a salt and water
* salt: a compound formed from the anion of the acid and cation of the base