ACS General Chemistry Practice Test 4

Correct: (D)

Radius decreases across a period; C is furthest right, so it is smallest.

Correct: (A)

Na has a single valence electron far from the nucleus; IE1 increases across the period (with Al slightly below Mg due to its 3p electron).

Correct: (C)

Fewest protons (8) means weakest nuclear attraction, so O2- is largest.

Correct: (B)

Fe is [Ar]4s2 3d6; removing three electrons takes the 4s electrons first, then one 3d: [Ar]3d5.

Correct: (B)

Electronegativity increases up and to the right; F is the most electronegative element.

Correct: (C)

Mn2+ is [Ar]3d5; by Hund's rule all five d electrons are unpaired.

Correct: (A)

Five bonding domains with no lone pairs give a trigonal bipyramidal arrangement.

Correct: (D)

CO2 is linear, so the two C=O bond dipoles cancel; the others are bent or pyramidal.

Correct: (C)

O2 has a double bond: (10 bonding – 6 antibonding)/2 = 2.

Correct: (A)

N2 has a triple bond (bond order 3); O2 is double, F2 and Cl2 are single.

Correct: (B)

Three bonding domains and no lone pairs give trigonal planar sp2 hybridization.

Correct: (A)

Bond length decreases with increasing bond order; the single bond is longest.

Correct: (B)

The carbonate ion has three equivalent resonance structures with the π electrons delocalized over all three C-O bonds.

Correct: (B)

40.1 (Ca) + 12.0 (C) + 3(16.0) (O) = 100.1 g/mol.

Correct: (C)

2.0 mol × 6.022 × 1023 atoms/mol = 1.2 × 1024 atoms.

Correct: (A)

40/12 = 3.33, 6.7/1 = 6.7, 53.3/16 = 3.33; dividing by 3.33 gives 1:2:1, so CH2O.

Correct: (D)

0.25 mol × 40.0 g/mol = 10 g.

Correct: (B)

3.0 g H2 = 1.5 mol; 32 g O2 = 1.0 mol. O2 requires 2.0 mol H2, but only 1.5 mol is present, so H2 limits.

Correct: (C)

2(+1) + S + 4(-2) = 0; S = +6.

Correct: (A)

M1V1 = M2V2; V1 = (0.50)(500)/2.0 = 125 mL.

Correct: (B)

By definition, one mole of an ideal gas occupies 22.4 L at 0°C and 1 atm.

Correct: (D)

NH3 has the strongest intermolecular forces (hydrogen bonding) and largest molecular volume effects, causing the greatest deviation.

Correct: (A)

PO2 = XO2 × Ptotal = (0.50/2.0)(1.0) = 0.25 atm.

Correct: (C)

KEavg = (3/2)RT; it depends only on temperature, not on identity, volume, or pressure.

Correct: (D)

CH4 has only weak London forces, so it evaporates most readily; the others hydrogen-bond.

Correct: (A)

ΔHf° is zero for elements in their standard states; compounds have nonzero values.

Correct: (C)

Positive ΔH means heat is absorbed; the reaction is endothermic.

Correct: (B)

18 g H2O = 1.0 mol; q = (1.0)(6.01) = 6.01 kJ.

Correct: (D)

Heat (q) depends on the path taken; enthalpy, entropy, and Gibbs energy depend only on the state.

Correct: (A)

q = (50)(4.18)(20) = 4180 J.

Correct: (B)

Combustion releases heat; the others absorb heat.

Correct: (A)

Energy increases with frequency; gamma rays have the highest frequency.

Correct: (D)

A d subshell has 5 orbitals, each holding 2 electrons: 10 total.

Correct: (C)

Radial nodes = n – l – 1 = 3 – 0 – 1 = 2 for the 3s orbital.

Correct: (B)

Δx · Δp ≥ h/4π; position and momentum cannot both be precisely known.

Correct: (C)

Rate ∝ [A]²; doubling gives 2² = 4 times the rate.

Correct: (A)

For rate (M/s) = k[A]0 = k, k has units of M·s-1.

Correct: (B)

The slowest (rate-determining) step acts as a bottleneck for the overall reaction.

Correct: (D)

Ea is the barrier height from the reactant level to the peak (transition state).

Correct: (C)

Each half-life halves the amount: (1/2)³ = 1/8 remains.

Correct: (A)

k depends on T, Ea, and catalyst, but not on concentrations (those appear separately in the rate law).

Correct: (B)

Kc = [products]coeff/[reactants]coeff = [SO3]²/([SO2]²[O2]).

Correct: (D)

At constant volume, an inert gas changes total pressure but not partial pressures or concentrations, so no shift occurs.

Correct: (A)

Heat is a product in an exothermic reaction; adding heat shifts equilibrium toward reactants, lowering K.

Correct: (C)

Pure solids are omitted from equilibrium expressions, leaving Kc = [CO2].

Correct: (B)

At equilibrium the system has no driving force in either direction, so ΔG = 0.

Correct: (D)

Large K indicates the product concentrations greatly exceed reactant concentrations at equilibrium.

Correct: (A)

Acid strength of binary acids increases down the group as the H-X bond weakens; HI is strongest.

Correct: (C)

Removing one proton from NH4+ gives NH3.

Correct: (B)

[H+] = 0.001 M, pH = 3.00, pOH = 14.00 – 3.00 = 11.0.

Correct: (C)

CO32- is the conjugate base of a weak acid and hydrolyzes to produce OH-; the others are neutral or acidic.

Correct: (D)

Equal concentrations give maximum resistance to pH change in both directions.

Correct: (B)

The salt formed (e.g., NaCl) does not hydrolyze, so the solution is neutral.

Correct: (A)

ΔGf° is zero for elements in their standard states.

Correct: (D)

Cu2+ has the higher reduction potential, so it gains electrons at the cathode.

Correct: (B)

A gas is produced from liquids, increasing molecular disorder.

Correct: (C)

Faraday's constant F = 96,485 C/mol e-.

Correct: (A)

The lead-acid battery's redox reaction is reversible; the others are primary (single-use) cells.

Correct: (D)

n → p + e-; the atomic number increases by 1 while the mass number is unchanged.

Correct: (B)

Graphite (and heavy water) slows neutrons without absorbing them; cadmium absorbs neutrons and lead is shielding.