Chem 238 Lab Questions with 100% Correct
Answers
Safety
What statement is correct about laboratory safety?
a. hot glass looks the same as cold glass
b. the silica gel from the TLC plates can have bad effects on your eyes
c. UV light is not good for your eyes
d. all of the above
D
Safety
If chemicals get into your eyes, the first thing you should do is to:
a. wash out your eyes in the eye wash station
b. run around the lab frantically
c. tell your T.A. about it
d. use the safety shower
A
Safety
If a strong acid comes into contact with your skin, wash the affected area with cold
water and apply:
a. dilute sodium acetate
b. dilute sodium bicarbonate
c. dilute sodium hydroxide
d. dilute sodium hydride
e. none of these
,B
UV Sunscreens
SPF refers to product effectiveness against the _____ rays of the sun.
a. UVA
b. UVB
c. UVC
d. UVA + UVB
e. UVA + UVB + UVC
B
UV Sunscreens
The organic compounds in sunscreen typically work because they _____ the ultraviolet
light that comes into contact with them.
a. deflect
b. reflect
c. absorb
d. none of the above
C
UV Suncreens
Beer's Law formula is:
a. c=elA
b. A=el/c
c. Ae=lc
d. A=elc
e. Al=ec
,D
UV Sunscreen
Which of the following UV rays can penetrate the Earth's atmosphere?
a. UVA
b. UVA and UVB
c. UVA and UVC
d. UVB and UVC
e. UVA, UVB, and UVC
B
UV Sunscreen
When a molecule absorbs visible or UV light, which of the following transitions takes
place?
a. electrons in lower molecular orbitals are excited into orbitals of higher energy
b. electrons in molecular bonds are excited from lower vibrational states to higher
vibrational states
c. atomic nuclei are excited from lower nuclei states to higher ones
d. molecules are excited from lower rotational states to higher ones
e. none of these
A
UV Sunscreen
Which of the following statements about the SPF, sunscreen protective factor, values for
sunscreens is false?
a. you should choose the SPF based on your skin type and the amount of time you plan
to
, be in the sun
b. SPF refers to product effectiveness against both UVA and UVB radiation
c. as SPF values increase, you get better UVB protection for the same amount of time in
the sun
d. as SPF values increase you can stay longer in the sun before you start getting
sunburn
e. SPF = (MED for the skin with sunscreen)/(MED for skin without sunscreen), where
MED
is minimal erythemal dose
B
UV Sunscreen
To obtain the UV spectra of sunscreen ingredients, we dissolve the samples in:
a. ethanol
b. hexanes
c. water
d. methanol
e. isopropyl alcohol
E
UV Sunscreen
An unknown substance exhibits an absorbance of 0.735 in a 1 cm cuvette. Previous
experiments showed that this unknown has a molar absorptivity coefficient of 53,000 at
340 nm. Determine the molar concentration of the unknown.
a. 0.00139 X 10^-3
b. 0.1401 X 10^-3
Answers
Safety
What statement is correct about laboratory safety?
a. hot glass looks the same as cold glass
b. the silica gel from the TLC plates can have bad effects on your eyes
c. UV light is not good for your eyes
d. all of the above
D
Safety
If chemicals get into your eyes, the first thing you should do is to:
a. wash out your eyes in the eye wash station
b. run around the lab frantically
c. tell your T.A. about it
d. use the safety shower
A
Safety
If a strong acid comes into contact with your skin, wash the affected area with cold
water and apply:
a. dilute sodium acetate
b. dilute sodium bicarbonate
c. dilute sodium hydroxide
d. dilute sodium hydride
e. none of these
,B
UV Sunscreens
SPF refers to product effectiveness against the _____ rays of the sun.
a. UVA
b. UVB
c. UVC
d. UVA + UVB
e. UVA + UVB + UVC
B
UV Sunscreens
The organic compounds in sunscreen typically work because they _____ the ultraviolet
light that comes into contact with them.
a. deflect
b. reflect
c. absorb
d. none of the above
C
UV Suncreens
Beer's Law formula is:
a. c=elA
b. A=el/c
c. Ae=lc
d. A=elc
e. Al=ec
,D
UV Sunscreen
Which of the following UV rays can penetrate the Earth's atmosphere?
a. UVA
b. UVA and UVB
c. UVA and UVC
d. UVB and UVC
e. UVA, UVB, and UVC
B
UV Sunscreen
When a molecule absorbs visible or UV light, which of the following transitions takes
place?
a. electrons in lower molecular orbitals are excited into orbitals of higher energy
b. electrons in molecular bonds are excited from lower vibrational states to higher
vibrational states
c. atomic nuclei are excited from lower nuclei states to higher ones
d. molecules are excited from lower rotational states to higher ones
e. none of these
A
UV Sunscreen
Which of the following statements about the SPF, sunscreen protective factor, values for
sunscreens is false?
a. you should choose the SPF based on your skin type and the amount of time you plan
to
, be in the sun
b. SPF refers to product effectiveness against both UVA and UVB radiation
c. as SPF values increase, you get better UVB protection for the same amount of time in
the sun
d. as SPF values increase you can stay longer in the sun before you start getting
sunburn
e. SPF = (MED for the skin with sunscreen)/(MED for skin without sunscreen), where
MED
is minimal erythemal dose
B
UV Sunscreen
To obtain the UV spectra of sunscreen ingredients, we dissolve the samples in:
a. ethanol
b. hexanes
c. water
d. methanol
e. isopropyl alcohol
E
UV Sunscreen
An unknown substance exhibits an absorbance of 0.735 in a 1 cm cuvette. Previous
experiments showed that this unknown has a molar absorptivity coefficient of 53,000 at
340 nm. Determine the molar concentration of the unknown.
a. 0.00139 X 10^-3
b. 0.1401 X 10^-3
