Chem midterm

Question 1

mole

Answer 1

an amount of substance that contains the same number of elementary entities as there are carbon-12 atoms in exactly 12g of carbon-12

*Prior to 2019, the mole was defined as 6.022 141 29 x 10^23 elementary entities

Question 2

Molecular mass

Answer 2

sum of atomic mass of each atom in the molecule (in u)

mass of one molecule
H2O: 18.0153u (or amu)

Question 3

Molar mass

Answer 3

Mass, in grams, of one mole of the substance

mass of one mole
H2O: 18.0153g (or g/mol)

Question 4

Percent composition

Answer 4

number of parts per 100 (cent) parts of the whole

ppt: parts per thousand
ppm: parts per million

Question 5

Empirical formula

Answer 5

Simplest whole number ratio of elements
CH3O

Question 6

Molecular formula

Answer 6

Exact number of atoms of each element
C2H6O2

Question 7

Structural formula

Answer 7

shows relative placement and connectivity of atoms
HO(CH2)2OH

Question 8

Stoichiometry

Answer 8

study of the quantitative aspects of chemical reactions.

Question 9

solution

Answer 9

homogeneous mixture of a solute dissolved in a solvent. If the solvent is H2O, this can be called an aqueous solution

Question 10

solute

Answer 10

dissolved substance present in the smallest amount in solution

Question 11

Solvent

Answer 11

dissolved substance present in the largest amount in solution

Question 12

Concentration

Answer 12

measure of the amount of solute in a solution

Question 13

Mass percent

Answer 13

m/m%
m solute/m solution = x g solute/100g solution

Question 14

volume percent

Answer 14

v/v% = x mL solute/100mL solution

Question 15

Mass/volume percent

Answer 15

m/v%
m solute/v solution = x g solute/ 100mL solution

Question 16

Molality

Answer 16

m or b
n solution/m solvent = x mol solute/1 kg solvent

Question 17

Mole fraction

Answer 17

x
nA/n total = x mol of “A”/1 mol solution

Question 18

ionic reactions

Answer 18

formation of a solid = precipitation reaction

transfer of electrons = redox reaction

transfer of a proton = acid-base reaction

Question 19

precipitation reactions

Answer 19

Molecular equation: species are written as intact compounds

ionic equation: more realistic, represents all species in their ionic forms
- spectator ions: ions that don’t get affected (same in both reactants and products side)

Net ionic equation: drops all of the spectator ions, only includes ions participating in the reaction

Question 20

Diatomic gases

Answer 20

H2, N2, O2 (also rarer, O3), F2, Cl2

Question 21

Monatomic gases

Answer 21

group 18

Question 22

gas

Answer 22

substance which is normally GASEOUS under
regular temperature and pressure conditions (example: oxygen gas at 25 degrees C)
pressure is created by the collisions of gas particles on surfaces (pressure = force/area)

Question 23

Vapour

Answer 23

gaseous form of a substance which is
normally LIQUID under regular temperature and pressure conditions (example: water vapour at 25 degrees C)

Question 24

Barometer

Answer 24

The pressure exerted by a gas is measured with a BAROMETER
Hg rises in tube until force of Hg (down) balances the force of atmosphere (pushing up).
Units = mmHg (Torr)

Question 25

Atmospheric pressure

Answer 25

pressure exerted by the column of air situated above a surface we do not feel this pressure because we are physiologically adapted to it

Question 26

Chemical dilutions

Answer 26

addition of one extra solvent to a solution does not change the number of moles of dissolved solute, so moles before = moles after dilution. n1=n2, c1v1=c2v2

Question 27

Homeopathy

Answer 27

Samuel Hahneman came up with a way to treat ailments with diluted solutions, which was later named homeopathy

Question 28

Molecular equation

Answer 28

species written as intact molecules in reality: they are dissociated ions AgNO3 + Nal -> Agl + NaNO3

Question 29

Ionic equation

Answer 29

More realistic than molecular equation represents all species in their ionic forms Ag(aq) + NO3(aq) + Na(aq) + I(aq) -> Agl(s) + Na(aq) + NO3(aq) Na and NO3 are spectator ions

Question 30

Net ionic equation

Answer 30

Drops spectator ions, so includes only those ions participating in the reaction. Ag + I -> AgI

Question 31

Oxidation state

Answer 31

form of electron bookkeeping charge on an atom if the bonding electrons were theoretically taken away (not shared) theoretical parameter

Question 32

How to assign oxidation number

Answer 32

12HFOX group 1 = +1 group 2 = +2 Hydrogen = +1 w nonmetals and -1 with metals/borons Fluorine= -1 Oxygen = -2 (UNLESS the other atom is more electronegative, or other atom is group 1 or 2, which makes oxygen -1 or +2) Group 17= -1 except with oxygen Follow highest rule first

Question 33

Atmospheric substance

Answer 33

A substance that can act as both acid and base (like H2O)

Question 34

Autoionization

Answer 34

acid-base reaction in which a proton is transferred between two identical amphoteric molecules

Question 35

What is Kw?

Answer 35

1x10^-14

Question 36

Anthocyanins

Answer 36

A naturally occurring class of molecules found in plants that change colours with a shift of equilibrium upon addition of acid or base

Question 37

What is a healthy pH level in blood?

Answer 37

7.35-7.45

Question 38

Ionization

Answer 38

When you have the conjugates in the products side, added water to acid/base

Question 39

Hydrolysis

Answer 39

When you have the conjugates in the reactants side, added water to conjugates

Question 40

True or false. An unknown solution of strong acid can be distinguished from an unknown solution of weak acid by measuring the pH of both solutions; the solution with the lower pH is the strong acid.

Answer 40

False. This is because pH depends on the strength and concentration. More concentration in acid = less pH

Question 41

True or false. Work energy for a gas is modeled by a state function.

Answer 41

False, depends on the path taken. internal energy, enthalpy, pressure, temperature, and volume) depend only on the initial and final states

Question 42

Four balloons are filled to the same volume with the following gases. If a small hole is made in each balloon while they are in the lab at atmospheric pressure and 15°C, which will deflate the fastest? a) SO2 b) H2S c) N2 d) CO2 e) None of these

Answer 42

1/(square root of molar mass). Represents the seconds. Whichever one is the lowest deflates faster.