Solutions and Concentrations
A chemistry student mixes 59 g of chloroform with 64 g of acetyl bromide and 46 g of acetone. What is the percent mass of chloroform?
35%
The osmotic pressure of a solution consisting of 111 mg of a protein dissolved in 5.00 mL of solvent is 0.0832 atm at 25 degrees C. What is the molar mass of the protein?
65.00 g/mol
Which of the following does not increase the rate constant?
a) increasing temp b) increasing the concentration of aqueous reactants c) introducing a catalyst d) introducing an intermediate e) introducing the pressure of gaseous reactants
d
2CO(g) + O2(g) <--> 2CO2(g)
2.0 x 104
What is the molecularity of the following elementary reaction?
2NO(g) + O2(g) --> 2NO2(g)
Termolecular
A student dissolves 18 g of phenol (C6H5OH, molar mass = 94.1040 g/mol) in 500.mL of a solvent with a density of 1.19 g /mL. What is the molality of this solution?
0.32 m
When 2.43 g of a certain molecular compound Z are dissolved in 55. g of cyclohexane (kf=20.8 C/m), the freezing point of the solution is measured to be 1.7 degrees C. Given that the normal freezing point of cyclohexane is 6.7 degrees C, what is the molar mass of compound Z?
180 g/mol
The following describes the oxidation of ammonia:
4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g)
If the rate of consumption of O2 is 10.0 M s-1, what is the relative rate of formation of NO?
8.0 M s-1
At a certain temperature, the following reaction follows first order kinetics with a rate constant of 0.0113 s-1.
2Cl2O5(g) --> 2Cl2(g) + 5O2(g)
Suppose a vessel contains Cl2O5 at a concentration of 0.790 M. Calculate the concentration of Cl2O5 in the vessel 68.0 s later.
0.37 M
Certain chemicals which used to be common in refrigerators and aerosols had the catastrophic effect of catalyzing the natural photodecomposition of ozone, causing a massive hole in the ozone layer. A proposed mechanism for this decomposition of ozone is:
Step 1: O3(g) + Cl(g) --> O2(g) + ClO(g)
Step 2: ClO(g) + O3(g) --> Cl(g) + 2O2(g)
Which species is a catalyst in this reaction mechanism?
Cl
A solution is made by mixing 131 g of heptane (C7H16, molar mass = 100.1926 g/mol) and 134 g of acetyl bromide (CH3COBr, molar mass = 122.946 g/mol). What is the mole fraction of heptane in this mixture?
0.545
At a certain temperature, the vapor pressure of pure benzene (C6H6; molar mass = 78.1046 g/mol) is measured to be 0.35 atm. A solution is prepared by mixing 112 g of benzene and 94.7 g of heptane (C7H16; molar mass = 100.1926 g/mol). What is the partial pressure of benzene vapor above this soluton?
0.21 atm
The rate of a certain reaction has the rate law: Rate = k[N2][H2]2
At a certain concentration of N2 and H2, the initial rate of reaction is 0.350 M/s. What would the initial rate of reaction be if the concentration of N2 is doubled?
0.700 M/s
CH3CO2C2H5(aq) + H2O(l) <--> CH3CO2H(aq) + C2H5OH(aq)
Kc = [CH3CO2H][C2H5OH] / [CH3CO2C2H5]
Suppose the reduction of nitrogen dioxide proceeds by the following mechanism:
Step 1: 2NO(g) --> N2O2(g) Rate constant = k1
Step 2: N2O2(g) + O2(g) --> 2NO2(g) Rate constant = k2
Suppose also k1<<k2, that is to say, the first step is much slower than the second step. Write the experimentally observable rate law for the overall chemical reaction.
Rate = k[NO]2
A certain substance X has a normal boiling point of 111.5 degrees celsius and a molal boiling point elevation constant Kb = 1.85 C/m. A solution is prepared by dissolving some urea (NH2)2CO; molar mass = 60.055 g/mol) in 350. g of substance X. The solution forms boils at 113.9 degrees C. What mass of urea was dissolved?
27 g
A certain liquid has a normal boiling point of 97.0 C and a boiling point elevation constant Kb = 0.74 C/m. A solution is prepared by dissolving some ammonium sulfate ((NH4)2SO4; molar mass = 132.14 g/mol) in 500. g of the liquid, and this solution boils at 98.1 C. What is the mass of (NH4)2SO4 that was dissolved?
30 g
The rate of a certain reaction has the rate law: Rate = k[NO]2[O2].
The rate of the reaction is measured to be 9.0 x 103 M/s when [NO] = 0.92 M and [O3] = 1.7 M. What is the value of the rate constant?
6.3 x 103 M-2 s-1
The rate constant of a certain reaction is known to obey the Arrhenius equation and to have an activation energy Ea = 38.0 kJ mol-1. If the rate constant of this reaction is 5.1 x 104 M-1s-1 at 330.0 C, what will the rate constant be at 293.0 C?
3.1 x 104 M-1s-1
Hydrogen chloride and oxygen react to form chlorine and water, like this:
4HCl(g) + O2(g) <--> 2Cl2(g) + 2H2O(g)
What is the correct concentration equilibrium constant expression for this reaction?
The molal freezing point depression constant Kf = 4.04 C/m for a certain substance Y. When 23.63 g of urea ((NH2)2CO); molar mass = 60.055 g/mol) are dissolved in 600. g of substance Y, the solution freezes at 3.6 degrees C. What is the normal freezing point of pure Y?
6.2 degrees Celsius
The rate at which a certain drug is eliminated by the body follows first-order kinetics, with a half-life of 45 minutes. Suppose in a particular patient the concentration of this drug in the bloodstream immediately after injection is 2.0 µg mL-1. What will the concentration be 180 minutes later?
0.13 µg mL-1
Given the following data, determine the rate law for the reaction:
Experiment [H2] (M) [I2] (M) Initial Rate (M s-1)
1 1.10 2.18 6.00 x 104
2 3.35 2.18 5.57 x 105
3 1.10 4.70 1.29 x 105
rate = k[H2]2[I2]
Phosphorus tribromide decomposes to form phosphorus and bromine, like this:
4PBr3(g) <--> P4(g) + 6Br2(g)
The pressure of the compounds at equilibrium is as follows:
PBr3 = 0.27 atm, P4 = 0.93 atm, Br2 = 1.7 atm
Calculate the value of the equilibrium constant, Kp, for this reaction.
4.2 x 103
At a certain temperature, the equilibrium constant Kc for the following reaction is 0.0055:
N2(g) + O2(g) <--> 2NO(g)
Calculate Kc for the reaction balanced as follows:
3N2(g) + 3O2(g) <--> 6NO(g)1.7 x 10-7