Chem 105
How many neutrons does 37Cl have?
20
Consider the reaction N2 (g) + 3H2 (g) ⇌ 2NH3 (g). Calculate the Kc for the reaction if the starting concentration of nitrogen gas is 1.0 M, the starting concentration of hydrogen gas is 3.0 M, and the equilibrium concentration of ammonia is 0.50 M.
Kc = 0.029
What is the sign of ΔSorxn for the reaction 2SO2 (g) + O2 (g) -- 2SO3 (g)?
Negative.
Consider the unbalanced reduction half-reaction MnO4- --> Mn2+. How many protons must be added in order to balance the hydrogens in acidic solution?
8
What type of nuclear reaction is indicated by the equation below?
²³⁸U → ²³⁴Th + ⁴He
Alpha particle decay.
How many oxygen atoms are in the compound calcium nitrate, Ca(NO3)2?
6
Consider the reaction 2NO2 (g) --> 2NO (g) + O2 (g). If the rate of appearance of oxygen gas is 0.20 M/s, what is the rate of disappearance of NO2?
0.40 M/s
What factors indicate increasing entropy in a system?
Temperature/volume increasing, phase changes (solid --> liquid --> gas).
What is the oxidation state of sulfur in H2SO4?
+6
The half life of iodine-131 is 8.0 days. If 80 g of iodine-131 is left to degrade, how much mass will remain after 24 days?
10 g
What is the correctly balanced equation for the combustion of propane, C3H8?
C3H8 + 5O2 --> 3CO2 + 4H2O
What is the reaction equation that corresponds to the equilibrium expression Kc = [NH3]2 / ([N2][H2]3)?
N2 + 3H2 ⇌ 2NH3
Consider the reaction 2NO2 (g) ⇌ N2O4 (g).
ΔHorxn = -58 kJ/mol
Under which temperature conditions is the reaction represented above spontaneous?
Low temperatures.
How many moles of electrons are produced from a current of 2.0 A in 1.0 hours?
0.075 mol
How long will it take for a 100. mg sample of carbon-14 to decay to 25 mg? The half-life of carbon-14 is 5730 years.
11,460 years.
The atomic weight of chlorine is 35.45 AMU, which is derived from the two naturally-occurring isotopes chlorine-35 (approximately 34.97 AMU) and chlorine-37 (approximately 36.97 AMU). What is the percent abundance of chlorine-35?
76.0%
Consider the reaction N2 (g) + 3H2 (g) ⇌ 2NH3 (g) at 298 K (ΔH = -92 kJ/mol; Ka = 6.0 x 10-2). If the concentration of ammonia decreases from 2.0 M to 1.0 M, what will happen to the equilibrium?
Equilibrium will shift to the right.
Consider the reaction N2 (g) + O2 (g) --> 2NO (g).
ΔH = +180 kJ/mol
ΔS = +25 J/mol·K
At what temperature does the reaction become spontaneous?
7200 K
Balance the reaction Fe2+ + Cr2O72- --> Fe3+ + Cr3+ in acidic solution.
6Fe2+ + Cr2O72- + 14H+ --> 6Fe3+ + 2Cr3+ + 7H2O
Polonium-210 is an alpha emitter with a half-life of 138 days. If a sample initially contains 10.0 mg of polonium-210, what mass is present after 414 days?
1.25 mg
What is the molecular shape and angle for each bond in carbon dioxide, CO2?
The pH of a solution is 3.24. What is the concentration of hydroxide ions in the solution?
Consider the reaction H2 (g) + Cl2 (g) --> 2HCl (g).
ΔH = -184 kJ/mol
ΔS = -20.0 J/mol·K
Calculate ΔG at 25oC and determine spontaneity.
178 kJ/mol
What is the standard potential of a voltaic cell with a zinc anode and a copper cathode in a solution of 1.0 M metal nitrates?
A researcher claims that an ancient scroll originated from Greek scholars in about 500 BC. A measure of its C-14 decay rate gives a value that is 30% of that found in living organisms. How old is the scroll?
9,953 years