Chem 238 Lab Final| Texas A & M University-College
Sta on
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 sta'on
b. run around the lab fran'cally
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 effec'veness 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 transi'ons takes place?
a. electrons in lower molecular orbitals are excited into orbitals of higher energy
b. electrons in molecular bonds are excited from lower vibra'onal states to higher vibra'onal
states
c. atomic nuclei are excited from lower nuclei states to higher ones
d. molecules are excited from lower rota'onal states to higher ones
e. none of these
A
, UV Sunscreen
Which of the following statements about the SPF, sunscreen protec've factor, values for
sunscreens is false?
a. you should choose the SPF based on your skin type and the amount of 'me you plan to
be in the sun
b. SPF refers to product effec'veness against both UVA and UVB radia'on
c. as SPF values increase, you get be4er UVB protec'on for the same amount of 'me in
the sun
d. as SPF values increase you can stay longer in the sun before you start ge5ng 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 cuve4e. Previous experiments
showed that this unknown has a molar absorp'vity coefficient of 53,000 at 340 nm. Determine
the molar concentra'on of the unknown.
a. 0.00139 X 10^-3
b. 0.1401 X 10^-3
c. 0.0040 X 10^-3
d. 0.0139 X 10^-3
D
UV Sunscreen
Which of the following items is false about the UV analysis of sunscreens experiment?
a. UV-Vis spectroscopy detects the electronic transi'ons of conjugated systems.
b. UV-Vis spectrum can be used to measure the concentra'on of some products.
c. SPF only refers to product effec'veness against the UVA rays of the sun.
d. Many sunscreen agents are composed of aroma'c rings in conjuga'on with other
Sta on
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 sta'on
b. run around the lab fran'cally
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 effec'veness 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 transi'ons takes place?
a. electrons in lower molecular orbitals are excited into orbitals of higher energy
b. electrons in molecular bonds are excited from lower vibra'onal states to higher vibra'onal
states
c. atomic nuclei are excited from lower nuclei states to higher ones
d. molecules are excited from lower rota'onal states to higher ones
e. none of these
A
, UV Sunscreen
Which of the following statements about the SPF, sunscreen protec've factor, values for
sunscreens is false?
a. you should choose the SPF based on your skin type and the amount of 'me you plan to
be in the sun
b. SPF refers to product effec'veness against both UVA and UVB radia'on
c. as SPF values increase, you get be4er UVB protec'on for the same amount of 'me in
the sun
d. as SPF values increase you can stay longer in the sun before you start ge5ng 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 cuve4e. Previous experiments
showed that this unknown has a molar absorp'vity coefficient of 53,000 at 340 nm. Determine
the molar concentra'on of the unknown.
a. 0.00139 X 10^-3
b. 0.1401 X 10^-3
c. 0.0040 X 10^-3
d. 0.0139 X 10^-3
D
UV Sunscreen
Which of the following items is false about the UV analysis of sunscreens experiment?
a. UV-Vis spectroscopy detects the electronic transi'ons of conjugated systems.
b. UV-Vis spectrum can be used to measure the concentra'on of some products.
c. SPF only refers to product effec'veness against the UVA rays of the sun.
d. Many sunscreen agents are composed of aroma'c rings in conjuga'on with other
