Chemistry (School & UG)
Q. What is the relationship between the rate constant and temperature for a reaction according to the Arrhenius equation?
A.
k = Ae^(-Ea/RT)
B.
k = Ea/RT
C.
k = RTe^(-Ea)
D.
k = A + Ea/RT
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Solution
The Arrhenius equation states that the rate constant k is related to temperature T and activation energy Ea by k = Ae^(-Ea/RT), where A is the pre-exponential factor.
Correct Answer: A — k = Ae^(-Ea/RT)
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Q. What is the relationship between the rate constant k and temperature T according to the Arrhenius equation?
A.
k increases with decreasing T
B.
k decreases with increasing T
C.
k increases with increasing T
D.
k is independent of T
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Solution
According to the Arrhenius equation, k increases with increasing temperature due to the exponential dependence on the negative activation energy divided by temperature.
Correct Answer: C — k increases with increasing T
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Q. What is the relationship between the rate of a reaction and the concentration of reactants in a first-order reaction?
A.
Rate is proportional to the square of the concentration
B.
Rate is inversely proportional to the concentration
C.
Rate is directly proportional to the concentration
D.
Rate is independent of the concentration
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Solution
In a first-order reaction, the rate is directly proportional to the concentration of the reactant.
Correct Answer: C — Rate is directly proportional to the concentration
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Q. What is the repeating unit in the polymer polystyrene?
A.
C6H5CH=CH2
B.
C8H8
C.
C6H5C(CH3)=CH2
D.
C6H5C2H4
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Solution
The repeating unit in polystyrene is derived from the monomer styrene, which has the formula C8H8.
Correct Answer: B — C8H8
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Q. What is the role of a back titration?
A.
To determine the concentration of a strong acid
B.
To analyze a sample that is difficult to titrate directly
C.
To measure the pH of a solution
D.
To separate components in a mixture
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Solution
Back titration is used to analyze samples that are difficult to titrate directly, by adding an excess of titrant and then titrating the unreacted titrant.
Correct Answer: B — To analyze a sample that is difficult to titrate directly
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Q. What is the role of a buffer in a titration involving a weak acid and a strong base?
A.
To increase the reaction rate
B.
To maintain a constant pH
C.
To enhance the solubility of the acid
D.
To provide a color change indicator
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Solution
A buffer helps maintain a constant pH during the titration, which is crucial for accurate endpoint determination.
Correct Answer: B — To maintain a constant pH
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Q. What is the role of a buffer solution in a titration?
A.
To maintain a constant pH
B.
To increase the reaction rate
C.
To provide a color change
D.
To dilute the solution
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Solution
A buffer solution helps maintain a constant pH during a titration, which is crucial for accurate measurements, especially in weak acid-strong base titrations.
Correct Answer: A — To maintain a constant pH
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Q. What is the role of a buffer solution in electrophoresis?
A.
To enhance the conductivity of the gel
B.
To maintain a constant pH during the separation
C.
To increase the size of the molecules
D.
To provide a source of ions
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Solution
A buffer solution maintains a constant pH during electrophoresis, which is crucial for the stability and separation of charged molecules.
Correct Answer: B — To maintain a constant pH during the separation
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Q. What is the role of a buffer solution in titration?
A.
To maintain a constant pH
B.
To increase the reaction rate
C.
To dilute the titrant
D.
To change the color of the solution
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Solution
A buffer solution helps maintain a constant pH during titration, which is crucial for accurate measurements.
Correct Answer: A — To maintain a constant pH
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Q. What is the role of a buffer solution?
A.
To change pH rapidly
B.
To maintain pH stability
C.
To neutralize acids only
D.
To neutralize bases only
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Solution
A buffer solution maintains pH stability by resisting changes in pH upon the addition of small amounts of acid or base.
Correct Answer: B — To maintain pH stability
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Q. What is the role of a catalyst in a chemical reaction?
A.
It increases the activation energy
B.
It decreases the activation energy
C.
It is consumed in the reaction
D.
It changes the equilibrium position
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Solution
A catalyst lowers the activation energy, allowing the reaction to proceed faster without being consumed.
Correct Answer: B — It decreases the activation energy
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Q. What is the role of a catalyst in electrophilic aromatic substitution reactions?
A.
To stabilize the product
B.
To generate the electrophile
C.
To increase the temperature
D.
To decrease the reaction time
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Solution
The catalyst in electrophilic aromatic substitution reactions, such as AlCl3 or FeBr3, is used to generate the electrophile that will react with the aromatic compound.
Correct Answer: B — To generate the electrophile
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Q. What is the role of a cathode in an electrochemical cell?
A.
It is where oxidation occurs.
B.
It is where reduction occurs.
C.
It is where the salt bridge connects.
D.
It is where the electrons are generated.
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Solution
The cathode is the electrode where reduction occurs, gaining electrons from the external circuit.
Correct Answer: B — It is where reduction occurs.
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Q. What is the role of a chelating agent in qualitative analysis?
A.
To increase solubility
B.
To stabilize metal ions
C.
To enhance color change
D.
To precipitate ions
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Solution
Chelating agents stabilize metal ions in solution, which can help in the identification and quantification of metal ions during qualitative analysis.
Correct Answer: B — To stabilize metal ions
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Q. What is the role of a ligand in coordination compounds?
A.
To donate electrons
B.
To stabilize the metal ion
C.
To increase solubility
D.
To act as a catalyst
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Solution
A ligand is a molecule or ion that donates electron pairs to a metal ion to form a coordination complex.
Correct Answer: A — To donate electrons
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Q. What is the role of a pH indicator in a titration for qualitative analysis?
A.
To measure the temperature of the solution
B.
To indicate the endpoint of the titration
C.
To separate ions in the solution
D.
To enhance the color of the solution
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Solution
A pH indicator changes color at a specific pH level, signaling the endpoint of the titration, which helps in identifying the presence of certain ions.
Correct Answer: B — To indicate the endpoint of the titration
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Q. What is the role of a pH indicator in a titration?
A.
To increase the reaction rate
B.
To provide a color change at the endpoint
C.
To stabilize the solution
D.
To dilute the reactants
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Solution
A pH indicator changes color at a specific pH range, signaling the endpoint of the titration.
Correct Answer: B — To provide a color change at the endpoint
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Q. What is the role of a reagent in a qualitative analysis?
A.
To increase the temperature of the reaction
B.
To change the color of the solution
C.
To provide a specific reaction with the target ion
D.
To dilute the sample
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Solution
Reagents are used to react with specific ions to produce observable changes, aiding in their identification.
Correct Answer: C — To provide a specific reaction with the target ion
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Q. What is the role of a salt bridge in an electrochemical cell?
A.
To connect the two electrodes
B.
To maintain charge balance
C.
To increase conductivity
D.
To provide a source of ions
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Solution
The salt bridge maintains charge balance by allowing ions to flow between the two half-cells, preventing charge buildup.
Correct Answer: B — To maintain charge balance
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Q. What is the role of a solvent in UV-Vis spectroscopy?
A.
To enhance the absorption of light
B.
To provide a medium for the sample
C.
To scatter light for better detection
D.
To change the wavelength of light
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Solution
The solvent serves as a medium for the sample, allowing light to pass through and interact with the analyte without interfering with the measurement.
Correct Answer: B — To provide a medium for the sample
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Q. What is the role of a titrant in a titration for qualitative analysis?
A.
To provide a color change
B.
To react with the analyte
C.
To stabilize the solution
D.
To dilute the sample
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Solution
The titrant reacts with the analyte to produce a measurable change, often indicated by a color change, which helps identify the analyte.
Correct Answer: B — To react with the analyte
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Q. What is the role of a titrant in a titration process?
A.
To react with the analyte
B.
To dilute the solution
C.
To stabilize the pH
D.
To measure absorbance
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Solution
The titrant is the solution of known concentration that reacts with the analyte to determine its concentration.
Correct Answer: A — To react with the analyte
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Q. What is the role of a titrant in a titration?
A.
To react with the analyte
B.
To dilute the solution
C.
To stabilize the pH
D.
To measure the volume
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Solution
The titrant is the solution of known concentration that reacts with the analyte to determine its concentration.
Correct Answer: A — To react with the analyte
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Q. What is the role of citric acid in food preservation?
A.
Antioxidant
B.
pH regulator
C.
Flavor enhancer
D.
Color stabilizer
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Solution
Citric acid acts as a pH regulator, helping to preserve food by creating an acidic environment that inhibits microbial growth.
Correct Answer: B — pH regulator
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Q. What is the role of electrophoresis in the analysis of biological samples?
A.
To separate ions based on their charge and size
B.
To measure the absorbance of light
C.
To quantify the concentration of gases
D.
To determine the boiling point of compounds
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Solution
Electrophoresis separates biological molecules, such as proteins and nucleic acids, based on their charge and size.
Correct Answer: A — To separate ions based on their charge and size
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Q. What is the role of hydrogen in fuel cells?
A.
To act as a catalyst
B.
To provide energy through combustion
C.
To produce electricity through a chemical reaction
D.
To store energy
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Solution
In fuel cells, hydrogen reacts with oxygen to produce electricity, water, and heat, making it a clean energy source.
Correct Answer: C — To produce electricity through a chemical reaction
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Q. What is the role of hydrogen in redox reactions?
A.
It is always oxidized.
B.
It is always reduced.
C.
It can act as both an oxidizing and reducing agent.
D.
It does not participate in redox reactions.
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Solution
Hydrogen can act as both an oxidizing agent and a reducing agent in various redox reactions.
Correct Answer: C — It can act as both an oxidizing and reducing agent.
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Q. What is the role of hydrogen in the process of hydrogenation?
A.
Oxidizing agent
B.
Reducing agent
C.
Catalyst
D.
Solvent
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Solution
In hydrogenation, hydrogen acts as a reducing agent, adding hydrogen to unsaturated organic compounds.
Correct Answer: B — Reducing agent
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Q. What is the role of indicators in titration for qualitative analysis?
A.
To increase the reaction rate
B.
To provide a color change at the endpoint
C.
To stabilize the solution
D.
To separate the ions
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Solution
Indicators are used in titrations to provide a visual color change at the endpoint, helping to identify the completion of the reaction.
Correct Answer: B — To provide a color change at the endpoint
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Q. What is the role of phospholipids in cell membranes?
A.
Energy storage
B.
Genetic information storage
C.
Structural integrity and barrier function
D.
Catalysis of biochemical reactions
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Solution
Phospholipids form the bilayer structure of cell membranes, providing structural integrity and acting as a barrier.
Correct Answer: C — Structural integrity and barrier function
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