1984 MCQ

If the equilibrium constant for the reaction above is 3.7 x 10^15, which of the following correctly describes the standard voltage and the free energy change for this reaction?

E is positive and G is negative

A cube of ice is added to some hot water in a rigid, insulated container, which is then sealed. There is no heat exchange with the surroundings. What has happened to the total energy and the total entropy when the system reaches equilibrium?

Energy remains constant; Entropy increases

Which of the following reactions does NOT proceed significantly to the right in aqueous solutions?

H2O + HSO4- = H2SO4 + OH-

On the basis of the information above, a buffer with a pH=9 can best be made by using

H2PO4 - + HPO4 2-

Which, if any, of the following species is in the greatest concentration in a 0.100 M solution of H2SO4 in water?

H3O+ ions

The liquefied hydrogen halides have the normal boiling points given above. The relatively high boiling point of HF can be correctly explained by which of the following?

HF molecules tend to form hydrogen bonds

The net ionic equation for the reaction that occurs during the titration of nitrous acid with sodium hydroxide is

HNO2 + OH- = NO2- + H2O

The addition of an oxidizing agent such as chlorine water to a clear solution of an unknown compound results in the appearance of a brown color. When this solution is shaken with the organic solvent methylene dichloride, the organic solvent layer turns purple. The unknown compound probably contains

I-

Which of the following species CANNOT function as an oxidizing agent?

I-

Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct?

It depends on the relative molecular masses of X, Y, and Z

Atoms of an element, X, have the electron configuration shown above. The compound most likely formed with magnesium, Mg, is

Mg3X2

Forms a compound having the formula KXO4

Mn

Which of the following molecules has the shortest bond length?

N2

Each of the following can act as both a Bronsted acid and a Bronsted base EXCEPT

NH4 +

No odor can be detected when a sample of the solution is added drop by drop to a warm solution of sodium hydroxide.

NH4 +

The silver electrode is made larger

No change in voltage occurs

Which of the following has a zero dipole moment?

PF5

The alkenes are compounds of carbon and hydrogen with the general formula CnH2n. If 0.561 gram of any alkene is burned in excess oxygen, what number of moles of H2O is formed?

0.040 mole

In a titration experiment based on the equation above, 25.0 mL of an acidified Fe2+ solution requires 14.0 mL of standard 0.050 M MnO4- solution to reach the equivalence point. The concentration of the Fe2+ in the original solution is

0.14 M

A 20.0 mL sample of 0.200 M K2CO3 solution is added to 30.0 mL of 0.400 M Ba(NO3)2 solution. Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after the reaction is

0.160 M

How many moles of NaF must be dissolved in 1.00 L of a saturated solution of PbF2 at 25 C to reduce the [Pb2+] to 1 x 10^-6 M?

0.20 mole

What number of moles of O2 is needed to produce 14.2 grams of P4O10 from P? (Molecular weight P4O10 = 284)

0.250 mole

What is the order of the reaction with respect to I-?

1

Which of the following represents a pair of isotopes?

1. Atomic number = 7; mass number = 13 2. Atomic number = 7; mass number = 14

When the skeleton equation above is balanced and all coefficients reduced to their lowest whole-number terms. what is the coeficient for H+ ?

10

The pH of 0.1 M ammonia is approximately

11

A sample of 9.00 grams of aluminum metal is added to an excess of HCl. The volume of hydrogen gas produced at standard temperature and pressure is

11.2 L

Which of the following represents the ground state electron configuration for the Mn3+ ion?

1s2 2s2 2p6 3s2 3p6 3d4

The salt bridge is replaced by a platinum wire

Voltage becomes zero and remains at zero

A 50-milliliter sample of a 2-molar Cd(NO3)2 solution is added to the left beaker

Voltage decreases but remains above zero

When the concentration of substance B in the reaction above is doubled, all other factors being held constant, it is found that the rate of the reaction remains unchanged. The most probable explanation for this observation is that

substance B is not involved in the rate-determined step of the mechanism, but is involved in subsequent steps.

When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled?

the pressure of the gas

The geometry of the SO3 molecule is best described as

trigonal planar

Gaseous atoms of which of the elements above are paramagnetic?

V, Co, and As only

What is the standard heat of formation of methane as calculated from the data above?

-75.8 kJ/mole

The reaction of silver metal and dilute nitric acid proceeds according to the equation above. If 0.10 mole of powdered silver is added to 10. milliliters of 6.0 molar nitric acid, the number of moles of NO gas that can be formed is

0.015 mol

If 0.060 faraday is passed through an electrolytic cell containing a solution of In3+ ions, the maximum number of moles of In that could be deposited at the cathode is

0.020 mole

If the acid dissociation constant, Ka, for an acid HA is 8 x 10 ̄4 at 25°C, what percent of the acid is dissociated in a 0.50-molar solution of HA at 25 °C?

4%

When 70. milliliter of 3.0 M Na2CO3 is added to 30. milliliters of 1.0 M NaHCO3 the resulting concentration of Na+ is

4.5 M

A student wishes to prepare 2.00 liters of 0.100-molar KIO3 (molecular weight 214). The proper procedure is to weigh out

42.8 grams of KIO3 and add H2O until the final homogenous solution has a volume of 2.00 L

The density of an unknown gas is 4.20 grams per liter at 3.00 atmospheres pressure and 127 °C. What is the molecular weight of this gas? (R = 0.0821 liter-atm / mole-K)

46.0

When the equation for the half-reaction above is balanced, what is the ratio of the coefficients OH-/CrO2-?

4:1

silicon dioxide, SiO2

A network solid with covalent bonding.

Consider the equilibrium above. Which of the following changes will increase the concentration of HgI4 2-?

Adding 6M HNO3

The net ionic equation for the reaction between silver carbonate and hydrochloric acid is

Ag2CO3(s) + 2H+ + 2Cl- = 2AgCl(s) + H2O + CO2(g)

A 27.0 g sample of an unknown hydrocarbon was burned in excess oxygen to form 88.0 g CO2 and 27.0 g H2O. What is a possible molecular formula of the hydrocarbon?

C4H6

Pi bonding occurs in each of the following species EXCEPT

CH4

the solution gives no apparent reaction with dilute hydrochloric acid

CO3 2-

The elements in which of the following have most nearly the same atomic radius?

Cr, Mn, Fe, Co

What is the net ionic equation for the reaction that occurs when aqueous copper (II) sulfate is added to excess 6 M ammonia?

Cu 2+ + 4NH3 = Cu(NH3)4 2+

Nitramide decomposes slowly in aqueous solution. This decomposition is believed to occur according to the reaction mechanisms above. The rate law for the decomposition of nitramide that is consistent with this mechanism is given by which of the following?

Rate = k([N2H2O2]/[H+])

Forms monatomic ions with 2- charge in solutions

S

Forms oxides that are common air pollutants and that yield acidic solution in water

S

For which of the following molecules are resonance structures necessary to describe bonding satisfactorily?

SO2

Two flexible containers for gases are at the same temperature and pressure. One holds 0.50 gram of hydrogen and the other holds 8.0 grams of oxygen. Which of the following statements regarding these gas samples is FALSE?

The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules

Which of the following is the most probable explanation for the variation in the student's results?

The pipette was not rinsed with the HCl solution

According to the rate law for the reaction, an increase in the concentration of hydronium ion has what effect on this reaction?

The rate of the reaction increases

Solid ethyl alcohol, C2H5OH

a molecular solid with hydrogen bonding

For the reaction A(g) = B(g) + C(g), the equilibrium constant Kp is 2 x 10^-4 at 25 C. A mixture of the three gases at 25 C is placed in a reaction flask and the initial pressures are PA=21 atm, PB=0.5 atm, and PC=1.0 atm. At the instant of mixing, which of the following is true for the reaction written?

delta G > 0

When the substances in the equation above are at equilibrium at pressure P and temperature T, the equilibrium can be shifted to favor the products by

decreasing the temperature

A compound is heated to produce a gas whose molecular weight is to be determined. The gas is collected by displacing water in a water-filled flask inverted in a trough of water. Which of the following is necessary to calculate the molecular weight of the gas, but does NOT need to be measured during the experiment?

vapor pressure of the water

current is allowed to flow for 5 minutes

voltage decreases but remains above zero

When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular

volume