Chemical Reaction | MCQs

Explanation

A burning candle is an example of all three states of matter:

• Solid: The wax is in a solid state.
• Liquid: The melted wax is in a liquid state.
• Gas: The vaporized wax and combustion products are in a gaseous state.

Explanation

To calculate the molarity, we need to calculate the number of moles of sodium chloride (NaCl) dissolved in 500 cm³ (or 0.5 L) of solution.

Molar mass of NaCl = 58.44 g/mol

Number of moles = mass / molar mass = 40 g / 58.44 g/mol ≈ 0.684 mol

Molarity = number of moles / volume (in liters) = 0.684 mol / 0.5 L ≈ 1.368 M

Rounded to one decimal place, this is approximately 1.4M.

Explanation

• Solubility is typically expressed in grams of solute per 100 grams of solvent, denoted as g/100g or g/100mL.
• This unit is called the percentage concentration or percentage composition.

Explanation

• When a saturated solution of KCl (potassium chloride) is heated, the solubility of KCl increases, allowing more KCl to dissolve in the solution.
• If the solution is heated to a temperature where all the KCl dissolves, it becomes a supersaturated solution.
• A supersaturated solution contains more dissolved solute than it can hold at a given temperature, making it unstable.

Explanation

• When the pressure on a gas increases, the molecules are forced closer together, resulting in a higher density.
• This is because the volume of the gas decreases as the pressure increases, causing the molecules to be more concentrated.

Explanation

• In the evaporation process, liquid molecules gain energy and move faster.
• It allowing them to escape from the surface of the liquid into the surrounding air.
• This occurs when the molecules have enough energy to overcome the intermolecular forces holding them to the surface.

Explanation

• One atmospheric pressure, also known as standard atmospheric pressure.
• It is defined as 101325 Pascals (Pa).
• This is the pressure exerted by the weight of the atmosphere at sea level.
• It is used as a standard unit of pressure.

Explanation

• Hydrogen (H2) is the lightest molecule, with a molecular weight of 2.016 g/mol.
• According to Graham's Law of Diffusion, the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.
• Therefore, hydrogen diffuses the fastest.

Explanation

• A covalent bond is a chemical bond formed by the mutual sharing of electrons between two atoms.
• This type of bond typically occurs between nonmetal atoms, such as in molecules and organic compounds.

Explanation

• When two identical atoms share electron pairs and exert an equal force on each other, the bond formed is a non-polar covalent bond.
• This type of bond is characterized by a equal sharing of electrons, resulting in a balanced and symmetrical distribution of electrons.