Gas Laws
The rate of effusion of helium to an unknown noble gas is 8.570. What is the identity of the unknown noble gas?
a). Kr
b). Xe
c). Og
d). Rn
c) Og - Oganesson (≈294 g/mol)
If a system releases heat, what is the sign of q?
Negative (q < 0)
What does it mean that the energy of an electron in an atom is quantized?
Energy can only exist at specific, discrete levels — not continuous values.
How many quantum numbers describe an electron?
4
Write the condensed configuration for Al (Z=13).
[Ne] 3s² 3p¹
What happens to the volume of a gas when pressure doubles at constant temperature?
It halves (Boyle’s Law).
A system absorbs 150 J of heat and does 65 J of work. What is ΔE?
ΔE = q + w = +150 + (–65) = +85 J
Calculate the energy difference between n=2 and n=3 in hydrogen (J).
ΔE = E3-E2 = 3.03×10-19J
Give possible ml values for l=2.
-2,-1,0,1,2
Which configuration violates the Pauli Exclusion Principle?
A) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
B) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
C) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹
D) 1s² 2s² 2p⁶ 3s² 3p⁷
D - 3p can only hold 6 electrons
A 3.00 L sample of gas at 25°C is heated to 100°C at constant pressure. What’s the new volume?
V2 = 3.00 × (373/298) = 3.76L
Calculate w (in J) when a gas expands from 1.2 L → 6.2 L against 1.05 atm.
w=−PΔV=−1.05×(5.0)=−5.25L⋅atm=−532J
Calculate the wavelength (in nm) of the photon emitted when an electron falls from n = 3 to n = 2 in hydrogen. (hint ΔE= 3.03×10-19 J)
λ=hc/ΔE = 6.56×10-7m = 656nm
For 3d orbitals, how many angular nodes exist?
2
Explain why Cr and Cu are exceptions to the Aufbau principle.
Half/full d-subshells are more stable; one 4s electron promoted to 3d.
Calculate the density(g/L) of CO₂ at 1.00 atm and 298K
d = PM/RT = (1)(44)/(0.0821)(298) =1.81g/L
A 2.55 g sample of metal absorbs 35.6 J, ΔT = 21.4°C. What is the metal’s specific heat capacity?
C=q/(mΔT)=35.6/(2.55×21.4)=0.65J/g°C
An electron in hydrogen falls from n = 6 → n = 2. What is the wavelength (in nm) of the photon emitted?
a) 410 nm
b) 486 nm
c) 434 nm
d) 656 nm
a) 410 nm
How many total electrons can be housed in the n = 5 shell?
a) 18
b) 32
c) 50
d) 72
c) 50
2.96 g Cd reacts with HCl, raising 695 mL soln from 23.5→71.7°C (Cp=4.19, ρ=1.05). Find q.
q = (730)(4.19)(48.2) = 1.47×105J
A 2.50 mol gas sample in 4.00 L at 300 K has a=2.32,b=0.0396. Find pressure using the van der Waals equation.
P≈14.9atm
When 1.00 g of fructose, C6H12O6(s), is burned in oxygen in a bomb calorimeter, the temperature of the calorimeter increases by 1.58 °C. If the heat capacity of the calorimeter and its contents is 9.90 kJ/°C, what is qrxn (in kJ/mol) for this combustion?
-2.82x103 kJ
Consider an electron in the n = 1 shell of the Bohr atom. What wavelength of light will be absorbed by the atom in order to promote the electron to the n = 4 shell?
a). 121.6 nm
b). 225.3 nm
c). 97.3 nm
d). 41.6 nm
c)
Which of the following sets of four quantum numbers is NOT ALLOWED?
a). n = 5, l = 1, ml = 0, ms = + 1/2
b). n = 2, l = 1, ml = - 1, ms = - 1/2
c). n = 3, l = 3, ml = 2, ms = + 1/2
d). n = 7, l = 4, ml = - 2, ms = - 1/2
c). n = 3, l = 3, ml = 2, ms = + 1/2 [l= 0 - (n-1)]
Calculate the root mean square velocity of a sample of butane (C 4 H 10 ) gas at 487 K. The molecular weight of butane is 58.12 g/mol
a). 45.4 m/s
b). 523 m/s
c). 14.5 m/s
d). 457 m/s
d). 457 m/s