Mixed Deck — All CART Topics Flashcards

If the products of a reaction have higher enthalpy than the reactants, the ΔH for the reaction is:

Answer: Positive

ΔH = H(products) – H(reactants); if products have higher enthalpy, ΔH is positive, indicating an endothermic reaction.

A chemist dissolves 58.44 g of NaCl (1 mole) in 500 g of water. Which of the following correctly describes the concentration of this solution?

Answer: 2.0 molal

Molality (m) is defined as moles of solute per kilogram of solvent. First, convert the mass of the solvent (water) from grams to kilograms: 500 g = 0.500 kg. Then, calculate the molality: Molality = moles of solute / kg of solvent = 1 mole NaCl / 0.500 kg H₂O = 2.0 m.

Which of the following single displacement reactions will occur spontaneously according to the metal activity series?

Answer: Zn(s) + CuSO₄(aq) →

A single displacement reaction occurs when a more reactive element displaces a less reactive element from a compound. According to the activity series, zinc (Zn) is more reactive than copper (Cu), so it will displace copper from copper(II) sulfate. In the other options, the elemental metals (Cu, Ag, Fe) are less reactive than the metal ions they would need to displace (Al³⁺, H⁺, Mg²⁺), so no reaction will occur.

Under which of the following conditions would a real gas be expected to deviate MOST from ideal gas behavior?

Answer: Low temperature and high pressure

Real gases deviate from ideal behavior because the assumptions of the Kinetic Molecular Theory (negligible particle volume and no intermolecular forces) break down. [23] At low temperatures, gas particles move slower and intermolecular forces become more significant. At high pressures, the particles are forced closer together, making their individual volumes a more significant fraction of the total container volume. Therefore, the combination of low temperature and high pressure causes the most significant deviation from ideal behavior.

Which of the following processes is endothermic?

Answer: Melting of ice

Melting requires heat input to break intermolecular forces, making it an endothermic process.

What particles make up an alpha particle?

Answer: 2 protons and 2 neutrons

An alpha particle is identical to a helium-4 nucleus, consisting of 2 protons and 2 neutrons, giving it a charge of +2.

In the reaction: 4Fe + 3O₂ → 2Fe₂O₃, what is the mole ratio of iron (Fe) to ferric oxide (Fe₂O₃)?

Answer: 4:2

The mole ratio between two substances in a balanced chemical equation is determined by their respective stoichiometric coefficients. For iron (Fe) and ferric oxide (Fe₂O₃) in the given reaction, the coefficients are 4 and 2, establishing a mole ratio of 4:2.

In a laboratory experiment, the reaction of 15.0 g of aluminum (Al) with excess hydrochloric acid (HCl) produced 1.55 g of hydrogen gas (H₂). What is the percent yield of hydrogen? The balanced equation is: 2Al(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂(g)

Answer: 92.3%

First, calculate the theoretical yield. Moles of Al = 15.0 g / 26.98 g/mol ≈ 0.556 mol. From the 2:3 mole ratio between Al and H₂, moles of H₂ = 0.556 mol Al × (3 mol H₂ / 2 mol Al) = 0.834 mol H₂. Mass of H₂ (theoretical) = 0.834 mol × 2.02 g/mol = 1.68 g. The percent yield is (Actual Yield / Theoretical Yield) × 100 = (1.55 g / 1.68 g) × 100 ≈ 92.3%.

In the balanced chemical equation 2H₂ + O₂ → 2H₂O, how many moles of water are produced when 3 moles of hydrogen gas react completely?

Answer: 3 moles

From the balanced chemical equation, 2 moles of H₂ produce 2 moles of H₂O, indicating a 1:1 mole ratio between hydrogen gas and water. Therefore, if 3 moles of hydrogen gas react completely, an equal amount, 3 moles, of water will be produced.

The reaction between aqueous silver nitrate and aqueous sodium chloride produces solid silver chloride and aqueous sodium nitrate. How is this reaction best classified? AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

Answer: Double Displacement (Precipitation)

This reaction is a double displacement (or metathesis) reaction because the cations (Ag⁺ and Na⁺) and anions (NO₃⁻ and Cl⁻) from the two reactant compounds exchange partners to form two new compounds. Since one of the products, AgCl, is an insoluble solid (a precipitate), it is also specifically classified as a precipitation reaction.

A balloon contains 5.0 L of air at 27°C. If the pressure remains constant, to what temperature in Celsius must the balloon be heated to expand its volume to 8.0 L?

Answer: 207°C

This problem requires the use of Charles's Law, which describes the direct relationship between the volume and absolute temperature of a gas at constant pressure (V₁/T₁ = V₂/T₂). [7, 8] First, convert the initial temperature to Kelvin: T₁ = 27°C + 273.15 = 300.15 K. Then, rearrange the formula to solve for the final temperature (T₂): T₂ = (V₂ * T₁) / V₁. Plugging in the values: T₂ = (8.0 L * 300.15 K) / 5.0 L = 480.24 K. Finally, convert the temperature back to Celsius: T₂ = 480.24 K - 273.15 = 207.09°C.

What is the law that states that mass is neither created nor destroyed in a chemical reaction?

Answer: Law of Conservation of Mass

The Law of Conservation of Mass states that in any closed system, mass is neither created nor destroyed during a chemical reaction. This fundamental law means that the total mass of the reactants must equal the total mass of the products.

A chemist completely reacts 13.08 g of zinc metal (Zn) with an excess of hydrochloric acid (HCl) according to the balanced equation: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g). What volume of hydrogen gas (H₂) is produced at Standard Temperature and Pressure (STP)? (Molar mass of Zn = 65.38 g/mol)

Answer: 4.48 L

First, convert the mass of zinc to moles: 13.08 g Zn / 65.38 g/mol = 0.200 mol Zn. The mole ratio between Zn and H₂ is 1:1, so 0.200 mol of H₂ is produced. At STP (0°C and 1 atm), one mole of any ideal gas occupies 22.4 L. Therefore, the volume is 0.200 mol H₂ × 22.4 L/mol = 4.48 L.

Which of the following best describes the mass number of an atom?

Answer: The sum of the protons and neutrons in the nucleus

The mass number (A) of an atom represents the total count of protons and neutrons residing in its nucleus. It provides an approximate measure of the atom's mass in atomic mass units, as electrons contribute negligibly to the overall mass.

Which of the following is a balanced equation for the combustion of methane (CH₄)?

Answer: CH₄ + 2O₂ → CO₂ + 2H₂O

To balance the combustion of methane (CH₄), the number of atoms for each element must be equal on both sides of the equation. One carbon atom on the left requires one CO₂ on the right. Four hydrogen atoms on the left require two H₂O on the right (2*2=4). This then results in four oxygen atoms on the right (2 from CO₂ + 2 from 2H₂O), which means two O₂ molecules are needed on the left (2*2=4).

A beta particle emitted during beta-minus decay is identical to which particle?

Answer: An electron

A beta-minus particle is a high-energy electron emitted when a neutron in the nucleus converts to a proton.

Isotopes of an element differ in the number of which subatomic particle?

Answer: Neutrons

Isotopes are atoms of the same element, meaning they share the same number of protons and thus the same atomic number. They differ in their mass number because they have varying numbers of neutrons in their nucleus, leading to different atomic masses.

Nuclear fusion requires extremely high temperatures primarily because:

Answer: High temperature provides energy to overcome the electrostatic repulsion between positively charged nuclei

Positively charged nuclei repel each other (Coulomb repulsion); extremely high kinetic energy (temperature) is needed for them to get close enough for the strong nuclear force to fuse them.

Which conservation law requires that the mass numbers balance in a nuclear equation?

Answer: Conservation of mass number and atomic number

In nuclear equations, both the total mass number (nucleons) and total atomic number (charge) must be equal on both sides of the equation.

Which of the following molecules is held together by a polar covalent bond?

Answer: H₂O

A polar covalent bond occurs when electrons are shared unequally between two atoms due to a difference in electronegativity. In H₂O, oxygen is significantly more electronegative than hydrogen, pulling the shared electrons closer to itself and creating partial negative and positive charges within the molecule.