#1
Which of the following is a characteristic of a chemical reaction?
Change in color
ExplanationIndication of a chemical change.
#2
What is the role of an acid in a chemical reaction?
To donate protons
ExplanationAcids contribute protons to the reaction medium.
#3
Which of the following is a chemical property?
Reactivity
ExplanationInherent behavior indicating how a substance undergoes reactions.
#4
Which of the following is a characteristic of a reversible reaction?
It can proceed in both forward and reverse directions
ExplanationCapability to undergo forward and reverse processes.
#5
What is the unit of concentration typically used for solutions?
Molarity
ExplanationConcentration measure expressed in moles per liter of solution.
#6
What is the purpose of a catalyst in a chemical reaction?
To provide an alternative reaction pathway with lower activation energy
ExplanationEnabling a faster reaction route with lower energy requirements.
#7
Which of the following is NOT a factor affecting reaction rate?
Phase of the reactants
ExplanationReaction rate unaffected by the physical state of reactants.
#8
Which of the following is a common example of a redox reaction?
Combustion of methane (CH4)
ExplanationMethane combustion involves oxidation and reduction.
#9
What happens to the pH of a solution when a strong acid is added to it?
pH decreases
ExplanationStrong acids increase hydrogen ion concentration, lowering pH.
#10
What is the balanced equation for the reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl)?
NaOH + 2HCl → NaCl + H2O
ExplanationBalanced representation of the neutralization reaction.
#11
What is the role of a catalyst in a chemical reaction?
To increase the rate of reaction
ExplanationFacilitates a faster reaction without being consumed.
#12
In the reaction: 2H2(g) + O2(g) → 2H2O(g), what is the limiting reactant when 3 moles of H2 and 2 moles of O2 are reacted?
O2
ExplanationReactant exhausted first, determining reaction extent.
#13
What is the principle behind the process of fractional distillation?
Fractionation
ExplanationSeparation based on differences in component volatility.
#14
Which statement about catalysts is true?
They provide an alternative reaction pathway with lower activation energy
ExplanationCatalysts lower the energy barrier for reactions.
#15
What does the term 'dynamic equilibrium' refer to in a chemical reaction?
The rate of the forward reaction is equal to the rate of the reverse reaction
ExplanationBalanced rates, though concentrations may change.
#16
What is the formula for calculating reaction rate?
Δ[Reactants] / Δt
ExplanationRate equals change in concentration over time.
#17
What does a negative value of Gibbs free energy (ΔG) indicate for a reaction?
The reaction is spontaneous
ExplanationSpontaneity indicated when Gibbs free energy is negative.
#18
In the reaction: 2Fe(s) + 3Cl2(g) → 2FeCl3(s), what is the oxidizing agent?
Cl2
ExplanationSpecies causing oxidation in another is the oxidizing agent.
#19
What is the definition of an acid according to the Arrhenius theory?
A substance that releases hydrogen ions
ExplanationAcids release hydrogen ions in aqueous solutions.
#20
According to Le Chatelier's principle, what happens to a system at equilibrium when there is an increase in pressure?
The equilibrium shifts to the side with fewer moles of gas
ExplanationShift in equilibrium to minimize impact of pressure change.
#21
What is the equilibrium constant expression (Kc) for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)?
[NH3]^2 / [N2][H2]^3
ExplanationMathematical representation of equilibrium concentrations.
#22
What is the effect of increasing the temperature on an endothermic reaction at equilibrium?
The equilibrium shifts to favor the products
ExplanationHeat absorption favors the endothermic direction.
#23
What is the effect of adding a catalyst to a reaction at equilibrium?
It has no effect on the equilibrium position
ExplanationCatalyst doesn't alter the equilibrium distribution.
#24
What is the effect of increasing the concentration of reactants on the rate of a reaction?
It increases the rate
ExplanationHigher reactant concentration accelerates the reaction.
#25
What is the function of a buffer solution?
To resist changes in pH
ExplanationBuffers maintain stable pH by resisting changes.