Gases, Liquids and Solids MCQs for MDCAT

Correct answer: C. H₂O > HF > NH₃ > HCl

Water has the highest boiling point among these liquids due to extensive hydrogen bonding, followed by HF, then NH3, with HCl (which lacks hydrogen bonding) boiling lowest.

Correct answer: D. 51 cm³

Using the combined gas law (P1V1/T1 = P2V2/T2) with the given initial conditions and STP as final conditions gives a volume of approximately 51 cm³.

Correct answer: D. Energy of activation

According to collision theory, the minimum energy required for colliding molecules to react successfully is called the activation energy.

Correct answer: A. Helium

Helium, being lighter and cheaper than argon, is commonly used to provide an inert shielding atmosphere in some welding processes, though argon is also widely used.

Correct answer: C. X=Alcohol, Y=Acetic Acid, Z=Ester

X (alcohol) and Y (acetic acid) both react with sodium metal to release hydrogen gas, and together they undergo esterification to form Z, a fruity-smelling ester.

Correct answer: A. Ethene

Ethene is commonly used for the artificial ripening of fruits. It is a plant hormone that triggers the ripening process in fruits. When fruits are exposed to ethene gas, it stimulates the production of enzymes responsible for ripening, such as cellulase and pectinase.

Correct answer: C. H2

Canal rays are positively charged ions that are produced in a discharge tube when a high voltage is applied across a gas at low pressure. These rays are defected by electric and magnetic fields, and their deflection depends on their charge-to-mass ratio. Hydrogen has the lowest atomic mass compared to Ar, Me, and He. Since, the mass-to-charge ratio determines the deflection of canal rays, the lighter the particles, the greater their deflection. Therefore, H2 produces the lightest canal ray particles among the given options.

Correct answer: A. Neon

Molar Mass: Approximately 20.18 g/mol.Density: Neon is a noble gas with a low molar mass, resulting in a low density compared to the other options. At room temperature and pressure, its density is around 0.9002 g/L, making it the least dense of the four gases listed.

Correct answer: D. Absent

In an ideal gas, it is assumed that the intermolecular forces between gas molecules are absent. This is a key assumption in the ideal gas law (PV = nRT).

Correct answer: B. 2.24 dm3

Option B is correct. The volume occupied by 3.2 g of oxygen gas at STP is 2.24 dm3. STP stands for standard temperature and pressure, defined as 0 °C (273.15 K) and 1 atm (101325 Pa). To find the volume of a gas at STP, we use the ideal gas law: PV = nRT. Here, P is the pressure in atm, V is the volume in L, n is the number of moles, R is the ideal gas constant (0.08206 L atm mol-1 K-1), and T is the temperature in K.Given 3.2 g of oxygen, we calculate the moles of oxygen using its molar mass (32 g/mol): n = m / M = 3.2 g / 32 g/mol = 0.1 mol. At STP, we plug the values into the ideal gas law:V = nRT / P = (0.1 mol)(0.08206 L atm mol-1 K-1)(273.15 K) / (1 atm) = 2.24 L. Thus, 2.24 L equals 2.24 dm3.Options A, C, and D are incorrect as they either miscalculate the volume based on the number of moles or present incorrect standard gas volumes.

Correct answer: B. BaSO4

The correct answer is Barium sulfate (BaSO₄), which crystallizes in the orthorhombic crystal system. This system has three mutually perpendicular axes that are of unequal lengths, a characteristic feature of orthorhombic crystals.In contrast, Lead chromate (PbCrO₄) is not correct as it belongs to the tetragonal system, characterized by one axis being longer than the other two, which are equal in length. Zinc oxide (ZnO) is classified under the hexagonal system, which features a different arrangement altogether, while Sodium hydroxide (NaOH) is cubic, with all axes equal. Thus, the only correct option that matches the orthorhombic classification is Barium sulfate.

Correct answer: E. Gout

Gout is a form of inflammatory arthritis caused by the buildup of uric acid crystals in the joints.