# Physical Sciences

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1. Does size of ion matter when considering freezing point depression/boiling point elevation?
No. Only the charge matters (i.e. Ag+ is different from Ca2+, but NO3- doesn't differ from Cl-)
2. Do resistors that come after a wire affect its current? What about its magnetic field?
Yes. Because total current is dependent on equivalent resistance. So current & magnetic field will be affected.
3. If given graph of y vs. x, what does the area under the curve represent?
y*x

I.e., if y = power and x = time, the area under the curve would represent energy.

(P=E/t)
4. All of the following are equal to Avogadro's number EXCEPT:

A. # of atoms in 22.4 liters of oxygen at STP
B. # of electrons in 96,845 C of electricity
C. # of sulfuric acid molecules used to make a 1 L soln of 2 N H2SO4.
D. # of atoms in 1 mole of He at STP
A. # of atoms in 22.4 liters of oxygen at STP
(this multiple choice question has been scrambled)
5. Which of the following procedures would be most useful in preventing the loss of capacity of a battery while in storage?
Determine if battery loses capacity when reactions move left or right. If left, then look for a procedure that will drive reactions to the right; or at least inhibit theĀ  reaction.
6. Which of the following procedures would be most useful in preventing the loss of capacity of a battery while in storage?
Keeping products from leaving so it can shift back.
7. The X-rays that doctors look at are, in fact, negatives of the shadow. Bones & connective tissue are usually light, while soft tissue is dark. This is because...
The greater relative concentration of heavy elements found in bones & connective tissue scatters more of the incident X-rays.

Why? Because it's like a visible light shadow - dark shadow indicates very few rays passed through body. Because the picture is a negative of a shadow, the light areas indicate absence of X-rays...because they've been scattered.

Heavy elements will scatter X-rays more effectively, bc heavy elements have higher atomic numbers
8. Why can't sound waves (longitudinal waves) be polarized?
Because their vibration isn't perpendicular to the propagation direction.
9. What is the polarization of a wave the result of?
The resolution of its vibration into a plane perpendicular to its propagation direction.
10. If transmission axes of P1 and P2 are perpendicular to each other (P1 and P2 are polarizers), what would be the effect of inserting a 3rd linear polarizer in between P1 and P2 with its transmission axis at a 45 degree angle with the other polarizers?

Intensity of light beam at point B would:
A. Increase
B. Decrease
C. Not change
D. Polarizer would have no effect on intensity/polarization at point B
A: The intensity of the light beam at point B would increase.

This is because intensity can't be less than zero, but there WILL be an effect!
11. When do you get negative Intensity of light?
Never.
12. When can you assume that all gases in a container have the same average translational kinetic energy?
If they're all at the same temperature.
13. The fact that the Earth is rotating about its polar axis affects the escape velocity from the surface of the planet. Taking into account the earth's rotation, how does Vesc at North Pole compare to Vesc Equator?

How about North Pole vs. South Pole?
Greater at North Pole compared to at the Equator.

Same at North Pole and South Pole.

This is because F=mw2r and and rpole< requator; so max centripetal force needed at equator. Gravity is the at both points, but at equator, requires the extra centripetal force to keep the particle on the surface, meaning that it wants to leave more, so lower vesc.
14. What is an acid buffer made of?
A weak acid and its conjugate base.
15. Which of the following factors will affect molar solubility of a gas in a reservoir?

I. pH of water
II. Temp of water
III. Partial pressure of gas
All 3.
16. A block is attached to a vertical spring and set into oscillation. Which of the following will increase the period of the resulting oscillations?

I. Increasing mass
II. Increasing amplitude of oscillation
III. Decreasing spring constant
I & III. Look at formula for period of SHM for spring.
17. What combination of acid and base gives a pH of 7, <7, and >7?
• pH = 7: Strong acid + strong base; weak acid + weak base
• pH>7: Strong base + weak acid
• pH <7: Strong acid + weak base
18. Define equivalent mass (weight)
Equivalent mass: the mass of an acid that yields one mole of H+ OR the mass of a base that reacts with one mole of H+.
19. Define coordination compounds
The product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coordinate covalent bonds.
20. If a rxn is exothermic, what happens if you increase the temperature?
The rxn will shift towards the left.
21. At what temperature does melting occur at? Why? When does temperature of melted object increase?
At a constant temperature. because a certain amount of energy (the latent heat of fusion) is needed to convert a substance from its solid state to liquid state.

Temp of melted object does not increase until ALL of the compound has melted.
22. Define latent heat

Where is this seen?
Latent heat: heat released/absorbed from a system without a change of temperature.

Phase change.
23. What will happen if a small amount of extra heat is applied to a metal at its exact melting temperature?
A small amount of metal will turn into liquid, with the temperature remaining the same (latent heat).
24. NaOH is standardized by titration against a pure sample of KHP. If the student did not remove all of the moisture from the KHP before the titration with NaOH, the molarity determined for the NaOH would be?

Too high? Too low? The same?
Too high.

This is because it's easy to make a KHP soln of high precision, so you can use it to measure the amount of NaOH needed. [NaOH] = [KHP]
25. What happens when you add NO3- or K+ to a saturated solution of KNO3? What law can you attribute this to?

How can you add more ions without creating a precipitate?
Since the saturated soln of KNO3 holds the max number of NO3- and K+ ions, the addition of either ion will form a solid (precipitate). common ion effect

26. What is condonsity?
The molar concentration of NaCl that has the same specific conductance (electrical) as the soln.
27. How do you calculate mole fraction of Compound A?
Number of moles of Compound A/total moles in soln
28. If you're dissolving a solid into water and temperature increases during the mixing process, what can you conclude about: (1) Change in enthalpy? (2) Change in Gibbs Free Energy? (3) Change in entropy?
Enthalpy decreases (bc heat is released), entropy increases (b.c its dissolving) and G increases because of G=H-TS and has to be negative.
29. What does fusion mean in general chemistry?
Melting
30. Which phase change is used to determine the heat of fusion for a pure substance?
Melting of solid or freezing of liquid to determine the heat of fusion of a pure substance.
31. What is the enthalpy (heat) of fusion?
The enthalpy of fusion is the change in enthalpy resulting from heating one mole of a substance to change its state from a solid to a liquid. The temperature at which this occurs is the melting point.
32. What is a necessary condition for providing an accurate estimate of the age of a rock through radioactive dating?
Gases must have remained trapped in rock only since its formation.
33. What happens if a positron is emitted? Absorbed?
If emitted, atomic number will decrease by 1.

If absorbed, atomic number will increase by 1.
34. What is the only effect of increasing photon frequency on ejected electrons?

What does number of ejected electrons depend on?
Photon frequency only affects kinetic energy of ejected electrons!

The number of ejected electrons depends on number of incident photons (1 for 1)
35. What will affect an electric field: increasing circuit resistance for a fixed current or increasing distance between electrodes?
Both will decrease electric field, but distance matters more!
36. What type of motion does a charged particle undergo in an electric field?
Acceleration
37. What happens when electrons are ejected from a cathode in a circuit?

Why?

What is the other effect of this?
Current flows through the circuit

Because electrons ejected from cathode are replaced by electrons from battery & anode.

The only effect on the apparatus of electron ejection from the cathode is the current in the circuit.
38. If the wavelength of an object is measured to be smaller than the wavelength determined in the lab, what can you assume? What if it's larger?
If smaller - object is moving towards you (Doppler shift)

If larger - object is moving away.
39. If a far-sighted person can see objects clearly no closer than 300 cm away, what is the min distance from a plane mirror such a person must be to see his reflection clearly?
150 cm.

This is because a plane mirror produces images behind its plane at a distance equal to the do in front of plane. So, it will look like 300 cm.
40. If a costant force is applied to a mass, what is the acc?
Also constant - so linear increase in speed.
41. What is the fundamental, resonant wavelength of a pipe open at both ends that is 1 m long and 0.1 m in diameter?
2 m.

This is because an open pipe has its fundamental, resonant wavelength at twice the length of the pipe.
 Author: emmayarewhy ID: 164188 Card Set: Physical Sciences Updated: 2012-07-29 01:08:41 Tags: mcat Folders: Description: physical sciences hodge podge stuff to know Show Answers: