Physical Chemistry - Basic Concepts

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Q1. Which of the following is not a characteristic of an endothermic reaction? (2023)

Solution:

Endothermic reactions absorb heat, feel cold, and have a positive ΔH; they do not release heat.

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Q2. What is the pH of a solution with a hydrogen ion concentration of 1 x 10^-3 M? (2019)

Solution:

pH = -log[H+] = -log(1 x 10^-3) = 3.

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Q3. What is the primary factor affecting the rate of a chemical reaction? (2022)

Solution:

All of the above factors affect the rate of a chemical reaction.

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Q4. Which of the following statements is true regarding exothermic reactions? (2021)

Solution:

Exothermic reactions release heat, resulting in a negative enthalpy change.

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Q5. What is the formula for calculating the number of moles of solute in a solution? (2023)

Solution:

Number of moles = Molarity x Volume (in liters).

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Q6. What is the standard temperature and pressure (STP) in Kelvin and atm? (2020)

Solution:

Standard temperature and pressure (STP) is defined as 273 K and 1 atm.

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Q7. In a reaction, if the concentration of reactants is doubled, what happens to the rate of reaction if the reaction is first order? (2023)

Solution:

For a first-order reaction, the rate is directly proportional to the concentration of reactants, so doubling the concentration doubles the rate.

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Q8. What is the relationship between the equilibrium constant (K) and the Gibbs free energy change (ΔG) at standard conditions? (2022)

Solution:

The relationship is given by ΔG = -RT ln(K), where R is the gas constant and T is the temperature in Kelvin.

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Q9. In a reaction, if the concentration of reactants is doubled, what happens to the rate of reaction if it is first order? (2023)

Solution:

For a first-order reaction, the rate is directly proportional to the concentration of the reactant, so doubling the concentration doubles the rate.

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Q10. Which of the following is not a characteristic of an ideal solution? (2019)

Solution:

An ideal solution has a constant boiling point and obeys Raoult's law, while variable composition is not a characteristic.