intro
Question 1:
What is the correct formula to calculate the density of any gas?
Topic: Density Calculation in Gases
Correct Answer: B) d = PM/RT
- The formula for calculating the density of a gas is derived from the Ideal Gas Law, which relates pressure (P), volume (V), number of moles (n), gas constant (R), and temperature (T) as PV = nRT.
- To find the density ('d'), we need to manipulate the Ideal Gas Law, resulting in d = PM/RT, where 'M' represents molar mass.
- Therefore, the correct answer is B) "d = PM/RT," reflecting the relationship between the density of a gas and its pressure, molar mass, gas constant, and temperature.
Question 2:
Which gas mixture does not comply with Dalton's law of partial pressures?
Topic: Dalton's Law of Partial Pressures
Correct Answer: D) NH3 and HCl
- Dalton's law of partial pressures states that in a mixture of non-reacting gases, the total pressure is the sum of the partial pressures of each individual gas.
- This law is only applicable to non-reacting gases, meaning gases that do not react with each other to form a new substance.
- In the given options, NH3 and HCl react to form NH4Cl. Therefore, this mixture does not comply with Dalton's law, making the correct answer option D) "NH3 and HCl."
Question 3:
What is the molecular weight of a gas that diffuses twice as fast as another gas with a molecular weight of 64?
Topic: Gas Diffusion and Molecular Weight
Correct Answer: A) 16
- The rate of diffusion of a gas is inversely proportional to the square root of its molar mass, according to Graham's law of diffusion.
- Therefore, a gas that diffuses twice as fast as another gas will have a molecular weight that is a quarter of the slower gas.
- Given that the slower gas has a molecular weight of 64, the faster gas will have a molecular weight of 16, making the correct answer option A) "16".
Question 4:
Which mathematical representation correctly illustrates Boyle's law?
Topic: Boyle's Law
Correct Answer: D) PV = k
- Boyle's law states that the pressure and volume of a gas have an inverse relation when the temperature is held constant.
- This law can be mathematically represented as PV = k, where 'P' is pressure, 'V' is volume, and 'k' is a constant.
- Therefore, the correct representation of Boyle's law is option D) "PV = k".
Question 5:
If a gas has a volume of 1dm³ and pressure of 2 atm, what would be its new volume when the pressure is increased to 6 atm while the temperature is held constant?
Topic: Gas Volume and Pressure Relationship
Correct Answer: B) 1/3 dm³
- The relationship between the volume and pressure of a gas at constant temperature is described by Boyle's law, which states that the product of pressure and volume is a constant (P1V1 = P2V2).
- Given that the initial volume (V1) is 1 dm³ and the initial pressure (P1) is 2 atm, and the final pressure (P2) is 6 atm, we can use Boyle's law to find the new volume (V2).
- Solving the equation 12 = 6V2, we find that V2 = 1/3 dm³. Hence, the correct answer is B) "1/3 dm³".
Question 6:
Which gas behaves most ideally at standard temperature and pressure (STP)?
Topic: Ideal Gas Behavior
Correct Answer: D) H2
- An ideal gas is a theoretical gas composed of a set of randomly moving, non-interacting point particles. Real gases approach this behavior at high temperatures and low pressures.
- Small, nonpolar molecules like hydrogen (H2) exhibit behavior closest to the ideal gas assumptions due to their small size and weak intermolecular forces.
- Hence, the correct answer is D) "H2".
Question 7:
Under what circumstances would gases deviate from ideal behavior?
Topic: Deviations from Ideal Gas Behavior
Correct Answer: D) Both B and C
- The ideal gas law provides a reasonable approximation of the behavior of many gases under many conditions, but it becomes less accurate at very high pressures and low temperatures.
- At high pressures and low temperatures, the assumptions of the ideal gas law (negligible volume of gas particles and no intermolecular forces) are not valid due to increased intermolecular interactions and the significant volume of gas particles.
- Therefore, gases deviate from ideal behavior under those circumstances, making the correct answer D) "Both B and C".
MCQs 8:
What is the volume of one mole of an ideal gas at a temperature of 546.3 K and pressure of 2 atm?
Topic: Volume of Ideal Gas
Correct Answer: C) 22.414 dm³
- At standard temperature and pressure (STP), which is 273 K and 1 atm, one mole of any gas occupies a volume of 22.414 dm³.
- When both the temperature and the pressure of the gas are doubled from STP, the volume of the gas remains unchanged, according to the ideal gas law.
- Hence, the correct answer is C) "22.414 dm³".
MCQs 9:
Which of the following gases behaves most ideally at standard temperature and pressure (STP)?
Topic: Gas Behavior at STP
Correct Answer: D) H2
- Ideal gases are theoretical gases that follow the ideal gas law perfectly. In reality, small and nonpolar molecules tend to behave more like ideal gases.
- Hydrogen (H2) is the smallest molecular gas and has no dipole moment, so it behaves closest to an ideal gas at standard temperature and pressure (STP).
- Therefore, the correct answer is D) "H2".
MCQs 10:
What is the process of direct conversion of a solid into a gas?
Topic: Sublimation Process
Correct Answer: B) Sublimation
- Sublimation is the process in which a solid, when heated, vaporizes directly without passing through the liquid phase. The vapors can then be condensed back into the solid state.
- This process does not involve boiling or evaporation, but rather a direct transition of a substance from a solid to a gas and vice versa.
- Therefore, the correct answer is B) "Sublimation".
MCQs 11:
Can an ideal gas obeying the kinetic theory of gases be liquefied under any conditions?
MCQs 12:
Which of the following has the same number of molecules at standard temperature and pressure (STP)?
Topic: Avogadro's Law
Correct Answer: D) 280ml of CO2 and 280cm³ of N2O
- According to Avogadro's law, equal volumes of all gases at the same temperature and pressure contain an equal number of molecules.
- Given that 280ml (which is equal to 280cm³) of CO2 and 280cm³ of N2O have equal volumes, they contain the same number of molecules at STP.
- Therefore, the correct answer is D) "280ml of CO2 and 280cm³ of N2O".
MCQs 13:
In Charles's law, which factor remains constant?
Topic: Charles's Law
Correct Answer: C) Pressure
- Charles's law states that the volume of a given amount of gas is directly proportional to its absolute (Kelvin scale) temperature at constant pressure.
- This means that while the volume and temperature may change, the pressure remains constant during this process.
- Therefore, the correct answer is C) "Pressure".
MCQs 14:
What are the standard conditions of temperature and pressure (STP)?
Topic: Standard Conditions of Temperature and Pressure (STP)
Correct Answer: A) 0°C and 1 atm
- The phrase "Standard Temperature and Pressure" (STP) refers to the agreed-upon conditions of 0°C (273.15 Kelvin) and 1 atmosphere (atm) of pressure.
- These are commonly used conditions for calculations in gas laws and are not the same as room temperature (25°C) or boiling point of water (100°C).
- Therefore, the correct answer is A) "0°C and 1 atm".
Question 15:
Under what conditions does a real gas obey the Van der Waals equation most closely resemble an ideal gas?
Topic: Van der Waals Equation
Correct Answer: B) Both constants "a" and "b" are small
- The van der Waals equation considers intermolecular attraction (constant 'a') and molecular size (constant 'b') for real gases.
- A real gas behaves more like an ideal gas when both 'a' and 'b' are small because the forces of attraction and molecular size are negligible.
- Therefore, the correct answer is B) "Both constants 'a' and 'b' are small".
Question 16:
When does a real gas deviate from ideal behavior?
Topic: Deviation of Real Gases from Ideal Behavior
Correct Answer: C) At low temperature and high pressure
- Real gases behave more like ideal gases at high temperatures and low pressures.
- However, at low temperatures and high pressures, the intermolecular forces become significant, causing deviations from ideal gas behavior.
- Therefore, the correct answer is C) "At low temperature and high pressure".
Question 17:
In which state of matter is the disorder of particles the greatest?
Topic: States of Matter and Disorder
Correct Answer: B) Steam at 100°C
- The disorder of particles, or entropy, tends to increase as we move from solid to liquid to gas states.
- Particles in the gaseous state, such as steam at 100°C, have the greatest disorder.
- Therefore, the correct answer is B) "Steam at 100°C".
Question 18:
What is the equivalent of one torr in other measurement units?
Topic: Pressure Measurement Units
Correct Answer: B) One millimeter of mercury (mm Hg)
- One torr is equal to one millimeter of mercury (mm Hg).
- It is not equivalent to one Pascal, 76 cm Hg, or one atmosphere.
- Therefore, the correct answer is B) "One millimeter of mercury (mm Hg)".
Question 19:
At constant pressure, what should the temperature be for the volume of a gas to become twice what it is at 0°C?
Topic: Gas Laws and Volume Changes
Correct Answer: C) 546 Kelvin
- According to Charles's law, at constant pressure, the volume of a gas is directly proportional to its absolute temperature.
- If the volume at 0°C (or 273 Kelvin) is x, it becomes 2x at a temperature twice 273 Kelvin, which is 546 Kelvin.
- Therefore, the correct answer is C) "546 Kelvin".
Question 20:
At what temperature does water begin to expand?
Topic: Anomalous Expansion of Water
Correct Answer: D) 4°C
- Water behaves exceptionally when it comes to temperature and expansion.
- Water starts to expand at 4°C due to the strengthening of hydrogen bonds below this temperature.
- Therefore, the correct answer is D) "4°C".
Question 21:
How would the volume of a gas change if its absolute temperature is doubled and the pressure is halved?
Topic: Ideal Gas Law
Correct Answer: B) Quadruples
- According to the Ideal Gas Law, the volume of a gas is directly proportional to its absolute temperature and inversely proportional to its pressure.
- If you double the temperature and halve the pressure, the volume of the gas will quadruple.
- Therefore, the correct answer is B) "Quadruples".
Question 22:
Which of the following is not true about gases?
Topic: Characteristics of Gases
Correct Answer: D) They do not mix well
- Gases are known for their ability to diffuse and mix easily due to the large distances between their particles.
- They have mass and are highly compressible, due to the large amount of space between particles that can be reduced under pressure.
- Therefore, the statement "They do not mix well" is not true about gases.
Question 23:
What do we call the temperature at which all molecular motion stops?
Topic: Absolute Zero
Correct Answer: A) Absolute Zero
- Absolute zero is a hypothetical temperature at which all molecular motion would stop. It's the lowest temperature possible.
- This temperature, absolute zero, is precisely 0 Kelvin, which is equivalent to -273.16°C or -459°F.
Question 24:
What volume does one mole of hydrogen gas occupy at standard temperature and pressure (STP)?
Topic: Molar Volume at STP
Correct Answer: B) 22.4dm³
- At STP (standard temperature and pressure), one mole of any gas occupies a volume of 22.4 liters or 22.4dm³. This is known as Avogadro's principle.
Question 25:
What is the standard value of the universal gas constant 'R'?
Topic: Universal Gas Constant
Correct Answer: B) 8.314 J mol⁻¹ K⁻¹
- The universal gas constant, often known as 'R', is a physical constant which appears in the equation of state of many gases. It has different units depending upon the circumstances.
- The standard SI unit for the gas constant is Joules per mole per Kelvin (J mol⁻¹ K⁻¹), and its value is 8.314.
Question 26:
How would you best describe the motion of gas particles?
Topic: Motion of Gas Particles
Correct Answer: D) Moving haphazardly in all directions
- The Kinetic Molecular Theory (KMT) states that gas particles move randomly, colliding with each other and the walls of their container, resulting in changes in their directions.
- The particles in a gas move randomly in all directions, and their motion can be represented as an average speed, while some will move slightly faster and others slightly slower.
Question 27:
Which gas law is understood only in terms of the Kelvin scale?
Topic: Gas Laws
Correct Answer: B) Charles’s law
- Charles’s law is the gas law that can only be properly explained using the Kelvin scale. This law cannot be adequately explained using the Celsius scale.
Question 28:
What is the number of molecules contained in one dm³ of CO at standard temperature and pressure (STP)?
Topic: Molecules in a Gas
Correct Answer: C) 2.68 × 10²²
- One mole of CO occupies 22.414dm³ and contains 6.02×10²³ molecules.
- Therefore, 1 dm³ of CO will contain (6.02×10²³/22.414) molecules of CO, which simplifies to 2.68×10²² molecules.
Question 29:
At what condition does a gas deviate the most from ideal gas behavior?
Topic: Gas Deviation from Ideal Behavior
Correct Answer: A) -10°C and 5 atm
- The deviation from an ideal gas behavior is typically observed at extreme conditions, like very low temperatures and high pressures.
- At these conditions, the attractive forces between gas molecules become prominent, and the volume of the molecules becomes a significant consideration.
Question 30:
How does a molecular collision, as per the Kinetic Theory of gases, affect energy?
Topic: Molecular Collisions and Energy Change
Correct Answer: A) No energy change
- According to the Kinetic Molecular Theory (KMT) of gases, the pressure exerted by a gas stems from the collisions of its molecules with the walls of the container.
- The molecular collisions are perfectly elastic according to the KMT, which means energy is conserved before and after the collisions.