EmSAT Chemistry Exam

Which factor does NOT affect solubility?

• Pressure

• Color of solvent

• Nature of solute

• Temperature

Answer explanation

The color of the solvent does not influence solubility. Factors like pressure, nature of solute, and temperature directly affect how well a solute dissolves, while color is irrelevant.

Which unit is used to measure mass in the SI system?

• Liter

• Second

• Meter

• Kilogram

Answer explanation

The SI unit for measuring mass is the kilogram. Other options like liter and meter measure volume and length, respectively, while second measures time. Therefore, the correct answer is kilogram.

Which term is used to describe the simplest ratio of elements in a compound?

• Empirical formula

• Isotopic formula

• Molecular formula

• Structural formula

Answer explanation

The empirical formula represents the simplest whole-number ratio of elements in a compound, distinguishing it from the molecular formula, which shows the actual number of atoms. Thus, the correct answer is empirical formula.

What is the concept of a mole based on?

• Avogadro's number

• Mass of a neutron

• Chemical reactivity

• Volume of gas

Answer explanation

The concept of a mole is based on Avogadro's number, which defines the number of particles in one mole of a substance, approximately 6.022 x 10^23. This is fundamental in relating mass to the number of atoms or molecules.

Which factor does NOT affect solubility?

• Pressure

• Color of solvent

• Nature of solute

• Temperature

Answer explanation

The color of the solvent does not influence solubility. Factors like pressure, nature of solute, and temperature directly affect how well a solute dissolves, while color is irrelevant.

Which element is located in Group 2 of the Periodic Table?

• Oxygen

• Helium

• Calcium

• Nitrogen

Answer explanation

Calcium is the correct answer as it is located in Group 2 of the Periodic Table, known as the alkaline earth metals. Oxygen, Helium, and Nitrogen are found in different groups.

Which law is used to calculate the overall enthalpy change in a reaction?

• Hess's law

• Boyle's law

• Newton's law

• Dalton's law

Answer explanation

Hess's law states that the total enthalpy change in a reaction is the sum of the enthalpy changes for individual steps, regardless of the pathway taken. This makes it the correct choice for calculating overall enthalpy change.

Which term is used to describe the simplest ratio of elements in a compound?

• Empirical formula

• Isotopic formula

• Molecular formula

• Structural formula

Answer explanation

The empirical formula represents the simplest whole-number ratio of elements in a compound, distinguishing it from the molecular formula, which shows the actual number of atoms. Thus, the correct answer is empirical formula.

What is the shape of a methane molecule?

• Square planar

• Tetrahedral

• Linear

• Trigonal planar

Answer explanation

A methane molecule (CH4) has a tetrahedral shape due to the four hydrogen atoms being symmetrically arranged around the central carbon atom, maximizing the distance between them. This arrangement minimizes repulsion, confirming the tetrahedral geometry.

Which term is used to describe the simplest ratio of elements in a compound?

• Empirical formula

• Isotopic formula

• Molecular formula

• Structural formula

Answer explanation

The empirical formula represents the simplest whole-number ratio of elements in a compound, distinguishing it from the molecular formula, which shows the actual number of atoms. Thus, the correct answer is empirical formula.