Chem-Phys (new)

Question 1

What is the equation for half life?

Answer 1

N(t) = N_0 (1/2)^(t/t_1/2})

N(t)	=	quantity of the substance remaining
N_0	=	initial quantity of the substance
t	=	time elapsed
t_{1/2}	=	half life of the substance

Question 2

How do you solve a fraction of a power?

Answer 2

fractions of powers

Question 3

What does mass number (superscript) refer too?

Answer 3

superscript refers to mass number (number of protons and neutrons)

Question 4

If a cell is placed in an environment with higher solute concentration than inside the cell, is it hypertonic or hypotonic?

Answer 4

If a cell is placed in an environment that contains a higher concentration of solutes than the interior of the cell, we call this environment hypertonic. When a cell is placed in a hypertonic solution, the solution is relatively solute-rich, while the cell is relatively watery. Therefore, water will move from the cell into the surrounding solution to equalize the solute concentration. This will cause the cell to lose water and shrink. In contrast, when a cell is exposed to a hypotonic (lower in solute concentration) environment, water will travel from the environment into the cell, causing the cell to swell and even burst, or lyse. Finally, an environment with the same solute concentration as the cell in question is termed isotonic.

Question 5

what happens to a liquid when the vapor pressure is equal to the atmospheric pressure?

Answer 5

When vapor pressure is equal to the atmospheric pressure exerted on the liquid’s surface, the liquid will boil. The more solute particles present, the lower the vapor pressure, and the higher the boiling point.

Question 6

What do the suffixes -ous and -ic in an ionic compund mean?

Answer 6

The ion with the lesser charge will use the suffix “-ous,” and the ion with the greater charge will use the suffix “-ic.” For example, the iron (II) cation, Fe2+, is termed the ferrous ion, while the iron (III) cation, Fe3+, is the ferric ion

Question 7

What do gamma rays represent?

Answer 7

Paragraph 3 mentions that the nuclei emit gamma rays, a form of electromagnetic radiation that consists of high-energy photons. Gamma rays represent ionizing radiation. The passage also states that I-131 undergoes β-minus decay. In β-minus decay, a neutron is converted to a proton as an electron is emitted. Therefore, iodine must be converted to an element with one additional proton, which can only be Xe

Question 8

How would you separate an acidic compound from a neutral one? (answer: extraction)

Answer 8

If all are liquids, one may be able to utilize distillation, which aims to separate liquids by utilizing the difference between their boiling points. If boiling points are very high, a vacuum may also be used to lower atmospheric pressure, which lowers the boiling points of all substances involved. Recrystallization is used to purify a solid product that contains impurities. Chromatography is a broad set of separatory techniques based on relative affinity, or tendency for a compound to attract to a certain solvent or structure. Finally, centrifugation utilizes a rapidly spinning apparatus to separate particles by density.

Question 9

What is the purpose of boiling chips? What is the purpose of vacuum distillation?

Answer 9

Boiling chips are used to provide nucleation sites that give the liquid a place to start forming bubbles to prevent superheating. Vaccum distillation lowers the boiling points of the substances to be distilled.

Question 10

What is the structure of (blank) functional group? (for all of them)

Answer 10

Know the structures of the functional groups

Question 11

What is the equation for kinetic energy?

Answer 11

KE = ½ mv2

Question 12

What is a tetrahedral stereocenter?

Answer 12

tetrahedral stereocenter = chiral center

Question 13

What is the equation for torque?

Answer 13

torque: τ = rFsin(Ɵ). Thus, there are three ways to increase the torque applied to an object: (1) increasing the force, (2) increasing the distance at which the force is applied from the fulcrum, and (3) adjusting the angle at which the force is applied to make it as close as possible to perpendicular to the lever arm.

Question 14

What is the equation for average velocity?

Answer 14

average velocity: v = d/t

Question 15

What does the equivalence point of a titration represent?

Answer 15

At equivalence points during the titration, the number of acid or base groups added to the solution is equivalent to the number of base/acid groups in the original unknown solution. We can calculate our unknown concentration or volume using the formula NaVa = NbVb, where N and V are the normality (mol/L) and volume of the acidic and basic solutions, respectively. It is important to convert from molarity (M) to normality (N) for polyprotic acids and polyvalent bases.

Question 16

What do Km and Vmax represent? What is the difference between competetive, noncompetetive, and uncompetetive inhibition?

Answer 16

Competitive inhibitors increase the Km of their associated enzymatic reactions without altering the Vmax value. Study Michaelis-Menten graphs

Question 17

What is the relationship between Ka pKa and pH?

Answer 17

Ka = [H+][A−]/[HA]

Question 18

What are Newtons 3 laws?

Answer 18

Newton’s third law can be expressed as: FA on B = −FB on A. Newton’s first law is a statement about inertia. It states that within a reference frame, an object remains at rest or at a constant velocity unless an external force acts upon it. Newton’s second law defines force. It states that the total sum of forces acting on an object is equivalent to its mass times its acceleration. This is the familiar equation Fnet = ma.

Question 19

What is the bond angle of a trigonal planar molecule?

Answer 19

Tetrahedral molecules contain four electron-rich areas and four bonded atoms, at angles of 109.5°. Trigonal pyramidal molecules likewise have four electron-rich areas, but only three are bonded atoms and the fourth is a lone pair. Bent molecules, like H2O, have two bonded atoms and two lone pairs. The bond angles in trigonal pyramidal molecules and bent molecules (107° and 104.5°, respectively) are slightly smaller than the 109.5° angle found in tetrahedral molecules. Trigonal planar molecules, like BF3, have three electron-rich areas and three bonded atoms at 120° angles, and linear molecules, such as CO2, have two electron-rich areas and two bonded atoms. Trigonal bipyramidal (e.g. PCl5) and octahedral molecules (e.g. SF6) have five and six electron-rich areas, respectively.

Question 20

How do you calculate resistance for resistors in series? In parallel? What is the equation for power?

Answer 20

Circuits can contain multiple resistors, which can be connected either in parallel or in series. For a circuit with resistors R1, R2, … Rn wired in series, Itotal = I1 = I2 = … = In, Vtotal = V1 + V2 + … + Vn, and Rtotal = R1 + R2 + … + Rn. If the resistors are wired in parallel, Itotal = I1 + I2 + … + In, Vtotal = V1 = V2 = … = Vn, and 1/Rtotal = 1/R1 + 1/R2 + … + 1/Rn.

Question 21

What are stong oxidizing agents? What are strong reducing agents?

Answer 21

The following features are associated with reduction in organic chemistry: (1) gain of an electron, (2) decreased oxidation state, (3) formation of a C–H bond (e.g. alkene → alkane), and (4) loss of a C–O or C–N bond (or any bond between carbon and an electronegative atom). Conversely, oxidation is associated with (1) loss of an electron, (2) increased oxidation state, (3) loss of a C–H bond (e.g. alkane → alkene), and (4) gain of a C–O or C–N bond (or any bond between carbon and a highly electronegative atom). A strong reducing agent, such as LiAlH4, can reduce a carboxylic acid directly to an alcohol, while weak reducing agents such as NaBH4 will not reduce carboxylic acids at all.

Question 22

What are the six primary classes of enzymes and what reactions do each carry out?

Answer 22

Oxidoreductases catalyze oxidation-reduction reactions where electrons are transferred. Transferases catalyze transfer of a chemical group from one molecule (donor) to another (acceptor). Lyases catalyze reactions where functional groups are added to break bonds in molecules or they can be used to form new double bonds or rings by the removal of functional group(s). Hydrolases catalyze reactions that involve cleavage of a molecule using water (hydrolysis). Ligases are used in catalysis where two substrates are stitched together (i.e., ligated) via the formation of C-C, C-S, C-N or C-O bonds while giving off a water (condensation) molecule.

Question 23

Where are the hydroxyl and carbonyl peaks on an IR spectroscopy graph?

Answer 23

The main peaks of an IR spectroscopy graph

Question 24

Between what side chains are disulfide links bonded? Why?

Answer 24

Disulfide linkages only form between the side chains of cysteine (C) residues.

Question 25

How do you calculate Ecell?

Answer 25

The tendency for a species to spontaneously become reduced is measured using a parameter called the standard reduction potential. Reduction potentials (E°) are measured in volts and are defined relative to the standard hydrogen electrode (2 H+ (aq) + 2 e- → H2(g)), which is set at 0 V. Greater (more positive) reduction potentials indicate that a substance ‘wants’ to be reduced more, while smaller (more negative) reduction potentials indicate that a substance is not prone to reduction.

Question 26

What conditions are met in a spontaneous reaction?

Answer 26

spontaneity is equivalent to ∆G < 0, Keq > 1, and E° > 0.

Question 27

How is total internal reflection achieved?

Answer 27

The angle of incidence always equals the angle of reflection. Light entering a more dense medium will bend towards the normal. With an angle of incidence of 30º, the angle of refraction must be less than 30º (II). Total internal reflection can only result when a ray of light begins in a higher-index material and reaches a boundary with a lower-index one (e.g. starting in water and moving towards air).

Question 28

Are polar molecules hydrophobic or hydrophilic?

Answer 28

If hydrophilic—that is, polar—residues are facing the aqueous solution, then water will be able to hydrogen-bond freely with those residues, meaning that it will have relatively high entropy, which is energetically favorable. In contrast, water molecules will not be able to hydrogen-bond effectively with nonpolar residues, and as a result will form a highly-ordered solvation shell to minimize interactions with those residues.

Question 29

Whar do capacitors and resistors do?

Answer 29

Capacitance is the ability to store charge and is calculated as C = ɛ0A/d, where A is the area of the plates and d is the distance between them.

Question 30

What is the equation of force?

Answer 30

Ff = mg sin θ

Question 31

What are the major characteristics of cancer cells?

Answer 31

cancer cells must develop the ability to bypass regulatory steps of the cell cycle that normally help to limit mitotic proliferation. In addition, malignant cells often undergo mutations that promote their own growth and the development of blood vessels to feed them (angiogenesis). The genes involved in oncogenesis can be divided into two groups: oncogenes and tumor suppressor genes. The basic difference between them is that oncogenes function to promote abnormal growth and proliferation, leading to cancer, while tumor suppressor genes function to prevent tumorigenic properties. Oncogenes can arise from the mutation of other genes, termed proto-oncogenes. If not mutated, proto-oncogenes do not promote cancer, but certain mutations or inappropriately elevated gene expression can effectively turn them into oncogenes.

Question 32

What makes peptide bonds stable?

Answer 32

Amino acids are linked together by peptide bonds, which involve the formation of an amide via the condensation of the –COOH group of one amino acid with the –NH2 group of another. Peptide bonds are quite stable under intercellular conditions, due in part to resonance stabilization; in addition to the form with a C=O double bond and a C–NH2 single bond, a resonance structure with a C–O– single bond and a C=N+H2 double bond exists. An important consequence of this resonance structure is that peptide bonds are planar and do not rotate freely, which helps contribute to the structural stability of three-dimensional polypeptide structures.

Question 33

What is hybridization?

Answer 33

when two nucleic acid strands bind to form a double-stranded structure, the process is termed hybridization, or annealing.

Question 34

If a reaction is spontaneous in one direction, is it also spontaneous in the reverse direction?

Answer 34

Read the passage carefully, if a rxn is spontaneous in one direction, it is nonspontaneous in the opposite direction

Question 35

What causes magnetic dipole moments?

Answer 35

Paramagnetic dipole moments are created from the magnetic dipole moment, which is a result of angular momentum from the intrinsic spin quality inherent in electrons

Question 36

What is the Aufbau principle?

Answer 36

The Aufbau principle says that electrons fill orbitals of the lowest energy first. Remember that energy increases as you go up the diagram

Question 37

What does mass spectrometry measure?

Answer 37

Mass spectrometry identifies proteins by mass-to-charge (m/z) ratio. Understanding that mass spectrometry ionizes the molecules in the sample and then measures their mass and charge is helpful in this question.

Question 38

What is beta-minus decay?

Answer 38

Beta-minus decay involves a neutron transforming into a proton. Since the total number of nucleons is the same, the atomic mass is still 131, however, there will be an increase in the number of protons by one. Because the atomic number has increased by one, the product is no longer Iodine-131, but Xenon-131.

Question 39

What is alpha decay?

Answer 39

According to the passage (and, ideally, your background knowledge), alpha decay involves the emission of a helium nucleus. Since helium has an atomic mass of 4 and an atomic number of 2, an alpha particle is two protons and two neutrons. These two isotopes clearly have a difference in mass of 4 (238 compared to 234), and only alpha decay can account for that.