What is the solubility product constant (Ksp) used for?
To measure the total mass of a solute that can dissolve in a solvent
To determine the concentration of a solute in a saturated solution
To calculate the solubility of a solute in a given solvent
To compare the solubilities of different solutes in the same solvent
Correct answer is B
The solubility product constant (Ksp) is a constant specific to a given solute and solvent at a particular temperature. It is used to calculate the concentration of a solute in a saturated solution, where no more solute can dissolve at equilibrium.
What is the chemical structure of soap and detergent molecules?
Hydrophilic head and hydrophobic tail
Hydrophilic head and hydrophilic tail
Hydrophobic head and hydrophobic tail
Hydrophilic tail and hydrophobic head
Correct answer is A
Both soap and detergent molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. The hydrophilic head allows the molecules to interact with water, while the hydrophobic tail interacts with oils and grease.
It becomes zero
It becomes negative
It remains the same
It becomes the reciprocal of the original value
Correct answer is D
If a reaction is reversed, the equilibrium constant (Kc) for the reversed reaction becomes the reciprocal of the original equilibrium constant. For a reaction:
A + B ⇌ C + D
The equilibrium constant Kc = [C][D]/[A][B]
For the reversed reaction:
C + D ⇌ A + B
The equilibrium constant Kc(reversed) = [A][B]/[C][D]
Thus, Kc(reversed) = 1/Kc.
Which of the following is an example of an endothermic reaction?
Combustion of propane (C\(_3\)H\(_8\)) to produce carbon dioxide (CO\(_2\)) and water (H\(_2\)O).
Burning of methane (CH\(_4\)) in the presence of oxygen
Formation of table salt (NaCl) from sodium (Na) and chlorine (Cl\(_2\)).
Decomposition of hydrogen peroxide (H\(_2\)O\(_2\)) into water (H\(_2\)O) and oxygen (O\(_2\)).
Correct answer is D
The decomposition of hydrogen peroxide (H\(_2\)O\(_2\)) into water (H\(_2\)O) and oxygen (O\(_2\)) is an endothermic reaction because it requires energy to break the bonds in the hydrogen peroxide molecule. The process absorbs heat from the surroundings to drive the reaction.
Who proposed the planetary model of the atom with electrons orbiting the nucleus?
Erwin Schrödinger
Ernest Rutherford
Niels Bohr
J.J. Thomson
Correct answer is C
Niels Bohr proposed the planetary model of the atom in 1913. According to this model, electrons move in circular orbits around the positively charged nucleus, much like planets orbiting the sun. However, this model has been refined in modern quantum theory.