Dr. Doe Chemical Quiz
Questions: 16 · 10 minutes
1. A fixed amount of ideal gas is kept at constant temperature. If its volume is halved, what happens to its pressure?
It falls to one-quarter of the original pressure
It falls to one-half of the original pressure
It doubles
It remains unchanged
2. Atoms that are isotopes of the same element differ in their number of what?
Protons
Neutrons
Valence-electron positions in the ground state
Nuclear charges
3. Drops of water tend to bead together on a waxed surface. Which interaction contributes most directly to the cohesion between water molecules?
Ionic attraction between H⁺ and O²⁻ ions
Hydrogen bonding between neighboring water molecules
Nonpolar attractions created by equal charge distribution
Metallic bonding among oxygen atoms
4. What is the usual effect of adding a catalyst to a reversible reaction at constant temperature?
It increases the equilibrium amount of product
It makes the forward reaction exothermic
It lowers the activation energy for both directions
It changes the reaction’s equilibrium constant
5. Compared with a solution at pH 5, a solution at pH 3 has what hydrogen-ion concentration?
100 times greater
Two times greater
100 times smaller
The same concentration
6. For the equilibrium A + B ⇌ C, additional A is introduced while temperature and volume remain constant. What response is expected as the system re-establishes equilibrium?
The reaction stops because the original equilibrium was disturbed
The system shifts toward A and B to create more reactants
The equilibrium constant increases to accommodate the added A
The system shifts toward C, consuming some of the added A
7. Why do elements in the same vertical group of the periodic table often undergo similar reactions?
They have the same number of occupied electron shells
They have similar valence-electron arrangements
They exist in the same physical state at room temperature
They have nearly identical atomic masses
8. In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, how does NH₃ act according to the Brønsted–Lowry definition?
As a base because it accepts a proton
As an acid because it produces OH⁻
As an acid because it gains positive charge
As a base because it donates an electron pair to OH⁻
9. What does an element’s atomic number represent?
The average number of neutrons across the element’s isotopes
The total number of protons and neutrons in each atom
The number of occupied electron shells in a neutral atom
The number of protons in each atom of the element
10. A student dilutes 100 mL of a 2.0 M solution until its total volume is 500 mL. What is the new concentration?
0.40 M
1.0 M
10 M
0.10 M
11. A solution contains 0.25 mol of solute in a total volume of 0.50 L. What is its molar concentration?
0.125 M
0.25 M
0.50 M
2.0 M
12. Which coefficient for O₂ balances the equation CH₄ + O₂ → CO₂ + 2H₂O?
1
2
3
4
13. Which type of bonding is primarily responsible for holding Na⁺ and Cl⁻ together in solid sodium chloride?
Ionic bonding
Hydrogen bonding
Nonpolar covalent bonding
Metallic bonding
14. An ion has 12 protons and 10 electrons. What is its net charge?
It is neutral, with a net charge of zero
It has a negative-two charge
It has a positive-two charge
It has a positive-twelve charge
15. On a potential-energy diagram, the products are lower in energy than the reactants. What does this indicate about the reaction?
It cannot proceed in the reverse direction
It is endothermic overall
It has no activation-energy barrier
It is exothermic overall
16. Approximately how many formula units are present in 0.50 mol of NaCl? Use Avogadro’s constant as 6.02 × 10²³ mol⁻¹.
1.20 × 10²⁴
8.30 × 10⁻²⁵
6.02 × 10²³
3.01 × 10²³