Chemistry 121S
Worksheet 1
Summer 2006
Oregon State University
Dr. Richard Nafshun
(13) 2. For each system below, give the signs (positive or negative) for w, q, and E:
(A)
A system does 10 kJ of work and gives off 220 kJ of heat.
(B)
A system does 50 kJ of work and absorbs 65 kJ of heat.
(C)
A system does 10 kJ of work and gives off 220 kJ of heat.
(D)
A system has 120 kJ of work done on it and gives off 50 kJ of heat.
(E)
A system has 70 kJ of work and gives off 85 kJ of heat.
(F)
A system does 75 kJ of work and gives off 75 kJ of heat.
(G)
A system cools down while expanding.
(H)
A system heats up a little while expanding a lot.
(I)
A endothermic reaction does not expand.
(14) 4. The heat of formation of urea, CO(NH2)2 (s) is –333.19 kJ/mol. Write the
chemical equation associated with this reaction (include phases—s, l, g, or aq).
5.
(Table 6.2 will be helpful) How much energy is given off when 8.00 moles of
CO (g) is formed from the elements (at 25 ˚C and 1 atm).
How much energy is given off when 500.0 g CO (g) is formed from the elements
(at 25 ˚C and 1 atm).
6.
Consider:
2 C8H18 (l) + 25 O2 (g) → 16 CO2 (g) + 18 H2O (l) ΔH˚reaction = -10900 kJ
How much energy is released when one mole of octane, C8H18, is combusted?
What is ΔH˚ when 9 moles of water are formed?
7.
(Table 6.2 will be helpful) Calculate ΔH˚ for the following reaction:
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (l) ΔH˚reaction = ?
8.
(Table 6.2 will be helpful) Calculate ΔH˚ for the following reaction:
C2H2 (g) + 5/2 O2 (g) → 2 CO2 (g) + H2O (l) ΔH˚reaction = ?
9.
The heat of formation of NH4Cl (s) is –315.4 kJ/mol. Write the chemical
equation associated with this reaction (include phases—s, l, g, or aq).
10.
From the following heats of reaction
2 SO2(g) + O2(g)  2 SO3(g)
H = – 196 kJ
2 S(s) + 3 O2(g)  2 SO3(g)
H = – 790 kJ
calculate the heat of reaction for
S(s) + O2(g)  SO2(g)
H = ? kJ
(1)
(2)
(3)
11.
Calculate the standard reaction enthalpy for the photosynthesis reaction,
o
6 CO2(g) + 6 H2O(l)  C6H12O6(s) + 6 O2(g) Hrxn
= ? kJ
The heat of formation of glucose, C6H12O6(s), is – 1274.5 kJ/mol; other values are listed in the
text.
12.
Given the following reactions and their enthalpy changes, calculate the enthalpy
change for
2 NO2(g) ----> N2O4(g)
Equations
Change in Heat Energy
N2(g) + 2 O2(g) ---> 2 NO2(g)
67.8 kJ
N2(g) + 2 O2(g) ---> N2O4(g)
9.67 kJ
(16) 1. What is meant by "quanta?"
2.
Sketch the entire electromagnetic (EM) spectrum with the highest energy on the
left. Label each region; gamma, x-ray, ultraviolet (UV), visible etc. Label the
highest and lowest energy regions. Label the highest and lowest frequency
regions. Label the longest and shortest wavelength regions. Does it make sense
that UV is to the left of visible? Explain. Which has a longer wavelength, blue or
red light? Which has a higher frequency, blue or red light? Which has a higher
energy, blue or red light?
3.
What is meant by "ROY G BIV?"
4.
Why is there a demand for blue lasers? What color is the laser in a CD player?
Which one (a blue or a red laser) has a shorter wavelength? Which one (a blue or
a red laser) has a greater energy?
5.
What is the color of light that has a wavelength of 532 nm? What is the
frequency of this light? What is the energy of one photon of this frequency?
What is the energy of one mole of photons of this frequency?
6.
What is meant by the ultraviolet radiation regions UVA (315-400 nm), UVB
(290-315 nm), and UVC (100-290 nm)? Which is most dangerous? Why?
7.
What is the wavelength, in nanometers, of light that has an energy content of 508
kJ/mol photons. In what portion of the electromagnetic spectrum will this light be
found? What portion of the electromagnetic spectrum lies to the right? Is this
portion higher or lower in energy?
8.
What is the wavelength (in meters) of the FM signal broadcast from KBVR radio
at a frequency of 88.7 MHz (88.7 x 106 Hz). Is this long or short compared to the
wavelength of the color you determined in Question #5?
Given that the energy level for the n = 1 level in the hydrogen spectrum is
-1312 kJ/mol, calculate the energy for the n = 2, n = 3, n = 4, n = 5, and n = ∞
levels.
kJ 

  1312

1
mol 
Recall, E is proportional to 2 . E = 
n


n2




9.
n
Energy (kJ/mol)
1
2
3
4
5
6
7
8
9
10
-1312.00
-328.00
-145.78
-82.00
-52.48
-36.44
-26.78
-20.50
-16.20
-13.12
10.
Which hydrogen atom has absorbed more energy; one in which the electron
moved from the first to the third energy levels or one in which the electron moved
from the second to the fourth energy levels? Explain.
11.
In the hydrogen atom, how much energy is required to remove one mole of
electrons from the n = 1 energy level? How much energy is required to remove
one mole of electrons from the n = 5 energy level? How much energy is required
to excite one mole of electrons from n = 1 to n = 3?
12.
How much energy is released from one mole of electrons when they relax from
n = 3 to n = 2? What is the wavelength and color of this emission?