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MCAT > General Chemistry > Flashcards

General Chemistry Flashcards

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MCAT flashcards
1
Q

Fundamental Unit Charge, known as an eV (electrons, protons)

A

1.6 x 10^-19 J

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2
Q

Atomic Number

A

Number of Protons in an element (determines what a substance is) For example, all Carbon have an atomic number of 6.

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3
Q

Mass Number

A

Number of Protons plus Number of Neutrons (Determines whether or not something is an isotope) For example, Carbon 14 has a mass number of 14 while Carbon 12 has a mass number of 12.

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4
Q

Mass in Grams of one AMU

A

1.66 x 10^-24 g

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5
Q

Atomic Weight

A

WEIGHTED average of the atomic masses for an element

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6
Q

Ernest Rutherford

A

Found that all atoms have a positively charged nucleus that account for very little of the atoms volume

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7
Q

Max Planck

A

Found that atoms can emit electromagnetic radiation in bundles of energy called quanta. This energy is calculated in his equation

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8
Q

Planck’s equation and constant

A 
E = hf
(h = 6.626 x 10^-34 j x s)
(f = frequency of the the radiation)
(E = energy)
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9
Q

Bohr Model

A

Bohr conceptualized that the electromagnetic radiation given off by atoms depends on the shells that the electrons moved between

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10
Q

Speed of light in a vaccum

A

3 x 10^8 m/s

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11
Q

Electromagnetic energy of an emitted photon can be determined with what equation?

A 
E = hc/λ
(E = energy)
(h = planck's constant)
(c = speed of light in a vaccum)
(λ = wavelength of the radiation)
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12
Q

The associated change in energy of an electron as it changes quantum numbers (n) can be determined with what equation?

A

E = Rh [1/ni^2 - 1/nf^2]

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13
Q

Value of Rydberg unit of energy

A

2.18 x 10^-18 j/e-
OR
13.6 eV

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14
Q

Heisenberg Uncertainty Principal

A

We can’t simultaneously know the momentum or where the heck electrons actually are

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15
Q

What two elements have a seemingly incorrect electron configurations due to Hund’s rule

A

Chromium and Copper both move electrons from lower principal quantum numbers because it is more favorable for electrons to be spinning in parallel

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16
Q

How do you find the maximum number of electrons in a given electron shell (n)

A

2n^2

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17
Q

Effective Nuclear Charge (Zeff)

A

A measure of the net positive charge experienced by valence electrons from the nucleus of an atom

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18
Q

Coordinate Covalent Bond

A

When one of the atoms involved in a covalent bond shares two electrons with another element (ex. Boron Tri-fluoride and ammonia)
-occur in acid/base reactions

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19
Q

Dipole Moment Equation

A 
p = qd
where...
 (p = dipole moment in debye units c/m)
 (q = magnitude of the charge)
 (d = displacement between the partial charges)
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20
Q

Difference between Electronic and Molecular geometries?

A

Electronic geometry refers to the arrangment of bonds and lone pairs around the central atom (i.e. tetrahedral) whereas molecular geometry refers to just the bonds and the EFFECT lone pairs have on them (i.e. trigonal pyramidal)

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21
Q

What is the differance between Formula weight and Molecular weight?

A

Formula weight is the total atomic weights of the atoms that make up a compound while molecular weight is the same thing but for only one molecule of that compound

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22
Q

Equivalents

A

How many moles of a certain compound will produce the thing we are interested in (electrons, H+)

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23
Q

Normality (N)

A

The concentration of 1 mole of an equivalent per liter found with the equation N = equivalent/L
(an example is a 1 N solution of a monoprotic acid will have 1 mole of H+ per liter fluid while the concentration of acid may be different)

24
Q

How would you find the molarity of something given the Normality

A

Molarity (M) = Normality/n

Where n = number of protons, electrons, etc,.

25
Q

Define the Arrhenius equation and explain how its used

A

k = Ae^ -Ea/RT
Where…
k is the rate constant (frequency of collisions resulting in a reaction)
T is the absolute temperature (in kelvins)
A is the frequency factor
Ea is the activation energy for the reaction (in the same units as RT),
R is the universal gas constant

This equation shows why an increase in temperature and a decrease in activation energy increases reaction rate!

26
Q

What are the four quantum numbers, what are there limits, and what does each represent?

A
  1. Is the principal quantum number (n) which can be conceptualized as the distance from the nucleus, and thus its energy level. This can be any number. There is a maximum of 2n^2 electrons in a shell.
  2. Is the azimuthal quantum number (l) which determines the shape of the orbital of the electron. This can be anything from 0 to n-1.
  3. Is the magnetic quantum number (ml) which is whether the electron is on the X,Y, or Z axis an electron is within a given shape. This can be anything -l to +l.
  4. Is the spin quantum number (ms) which determines the electron spin as either +1/2 or -1/2 which are the only two values.
27
Q

Which rule can be used to determine which electron shells will fill up first in an atom?

A

The n + l rule. If these are the same then the lower n is filled first. For example, 3s is filled after 2p.

28
Q

Method of memorizing what groups and rows refer to on the periodic table?

A

I remember groups of columns in Greek architecture and rows of periods when typing papers.

29
Q

For poly-atomic ions what do the roots: ate, ite, hypo, and per mean?

A

The LITEst anions have the fewest oxygens while the heaviest anions ATE the most oxygens. Hypo means less oxygens while per (hyper) has more oxygens.

30
Q

What is the difference between rate laws and equilibrium expressions in terms of what the compound coefficients become?

A

In equilibrium equations for K, the compounds coefficients become the exponents. In a rate law the exponents must be determined experimentally.

31
Q

The first law of thermodynamics can be used to find what?

A

It can be used to find the change in thermal energy of a system or the amount of energy lost via work or heat.
ΔU = Q - W

32
Q

Why does water have a negative slope of the solid-liquid line in its Phase Diagram?

A

Water has a negative slope because its solid state (ice) is less than its liquid state (water) thus an increase in pressure will actually melt ice.

33
Q

What equation would be used to find how much heat is produced in a reaction?

A 
q = mcΔt 
where: 
m = mass
c = specific heat
T = temperature in kelvin or Celsius
34
Q

What is the specific heat of water?

A

1 cal/gK OR 4.186 joules/ gram Celsius

35
Q

What is the equation for ΔG?

A

ΔG = ΔH - TΔS

36
Q

What equation would be used to find the change in free energy that occurs in a reaction?

A

ΔG = -RT lnKeq

37
Q

What equation would be used to find the number of moles of an IDEAL gas inside a room?

A

PV = nRT
where:
P = pressure (1 atm =760mmhg =760 torr = 101.325 kpa)
V = volume of container
n = number of moles
R = ideal gas constant (8.314 j/ K mol)
or (.0821 L atm/mol K)

38
Q

What equation would be used to compare the effects of changing variables on a gas?

A

P1V1 = P2V2

T1 T2

39
Q

What equation would be used to find the concentration of a gas at specific partial pressure?

A 
A = Kh x Pa
where:
A = the concentration of the gas
Kh = the henry constant (different for each gas)
Pa = the partial pressure of gas (A)
40
Q

Explain what compounds are water soluble?

A 
I use the NAG SAG mneumonic with a side of PMS and CASTRO BEAR
Always Soluble:
Nitrates 
Acetates
Group 1 nonmetals

Sulfates (Except PMS and CASTRO BEAR)
Ammonium
Group 17 (Except PMS)

41
Q

What is the molality of a solution with 12.01 grams of carbon and 1000 grams of water?

A

Molality = moles solute/ kg solution
= 1 mole C/ 1 kg solution
= 1 m

42
Q

What equation would be used to find the molarity of a new solution?

A

M1V1 = M2V2

43
Q

How would you estimate the pKa of an acid given the Ka of (1.8 x 10^-5)

A

The estimated Ka would be the 5 - .18

44
Q

What is the mnemonic for remembering what happens at the anode and cathode?

A

AN OX and a RED CAT
Anode = oxidation = loses electrons
Cathode = reduction = gains electrons

45
Q

What does a high Km value mean?

A

That the enzyme and substrate have a lower affinity

46
Q

What are the four colligative properties?

A
  1. Vapor pressure lowering
  2. Boiling point elevation
  3. Freezing point depression
  4. Osmotic pressure
47
Q

What is the relationship between vapor pressure lowering and boiling point elevation?

A

The lower the vapor pressure of a liquid, the higher its boiling point (ex. salt is placed in boiling water to have a colligative property effect of preventing more water molecules from escaping the water (vapor pressure lowering) which allows the water to boil at a higher temperature (boiling point elevation) and the food to cook faster)

48
Q

Is N2 an inert gas? Why?

A

It has a very stable structure formed by its lack of formal charges and a triple bond

49
Q

If the enthalpy of a system decreases and the spontaneity increases, is the delta G positive or negative?

A

negative (exergonic)

50
Q

If the enthalpy of a system increases and the spontaneity (entropy) decreases, is the delta G positive or negative?

A

positive (endergonic)

51
Q

If a system both loses enthalpy and entropy, at what temperatures will the reaction be exergonic?

A

Low temperatures

52
Q

If a system both increases enthalpy and entropy, at what temperatures will the reaction be exergonic?

A

High Temperatures

53
Q

What is a homotropic enzyme regulator?

A

Is an allosteric regulator and substrate of the enzyme that it reacts with (ex. O2 and Hb)

54
Q

How is an indicator selected for a titration?

A

An indicator with a pKa around the equivalence point of the titration is ideal

55
Q

What is a protease analog?

A

A substrate that mimics the substrate that the protease acts on thus inhibiting it

56
Q

Given pH what is a method of quantifying how many protons are present in solution?

A

pH = -log [H+] = 10^-pH

MCAT (8 decks)

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