Which of the following separation methods is based on the difference in boiling points?
A. Filtration
B. Decantation
C. Fractional distillation
D. Crystallization
Answer: C. Fractional distillation
Explanation: This method separates miscible liquids based on their different boiling points.
Question 7
The atomic number of an element is the number of ______ in its nucleus.
A. Neutrons
B. Protons
C. Electrons
D. Nucleons
Answer: B. Protons
Explanation: Atomic number is defined strictly by the number of protons.
Question 8
What is the oxidation number of Sulfur in SO2?
A. +2
B. +4
C. +6
D. -2
Answer: B. +4
Explanation: S + 2(-2) = 0. S - 4 = 0. S = +4.
Question 9
Which of the following is a greenhouse gas?
A. Oxygen
B. Nitrogen
C. Carbon (IV) oxide
D. Helium
Answer: C. Carbon (IV) oxide
Explanation: CO2 traps heat in the atmosphere, leading to the greenhouse effect.
Question 10
The gas produced when dilute HCl reacts with Magnesium metal is:
A. Oxygen
B. Chlorine
C. Hydrogen
D. Nitrogen
Answer: C. Hydrogen
Explanation: Active metals react with dilute acids to displace Hydrogen gas.
Question 11
A property of a pure substance that remains constant regardless of the sample size is:
A. Mass
B. Volume
C. Density
D. Weight
Answer: C. Density
Explanation: Density is an intensive property; it does not change based on how much material you have.
Question 12
The process of soap making is known as:
A. Esterification
B. Saponification
C. Fermentation
D. Polymerization
Answer: B. Saponification
Explanation: Saponification is the alkaline hydrolysis of fats or oils to produce soap.
Question 13
Which of the following allotropes of Carbon is the hardest known natural substance?
A. Graphite
B. Diamond
C. Coal
D. Lampblack
Answer: B. Diamond
Explanation: The tetrahedral arrangement of carbon atoms in diamond makes it extremely hard.
Question 14
The number of atoms in one mole of any substance is known as:
A. Atomic number
B. Avogadro's number
C. Mass number
D. Relative atomic mass
Answer: B. Avogadro's number
Explanation: Avogadro's constant is approximately 6.02 x 10^23 particles per mole.
Question 15
Which of the following indicators is colorless in acidic solution?
A. Methyl orange
B. Phenolphthalein
C. Litmus paper
D. Universal indicator
Answer: B. Phenolphthalein
Explanation: Phenolphthalein is colorless in acids and turns pink in bases.
Question 16
What is the functional group of Alkanols?
A. -COOH
B. -CHO
C. -OH
D. -CO-
Answer: C. -OH
Explanation: The hydroxyl group (-OH) is the characteristic group for alcohols.
Question 17
Which gas law relates volume and temperature at constant pressure?
A. Boyle's Law
B. Charles's Law
C. Avogadro's Law
D. Graham's Law
Answer: B. Charles's Law
Explanation: V1/T1 = V2/T2.
Question 18
Hard water contains dissolved ions of:
A. Sodium and Potassium
B. Calcium and Magnesium
C. Lead and Copper
D. Iron and Zinc
Answer: B. Calcium and Magnesium
Explanation: The presence of Ca2+ and Mg2+ ions prevents soap from lathering easily.
Question 19
The enzyme that breaks down starch into maltose is:
A. Pepsin
B. Lipase
C. Amylase
D. Trypsin
Answer: C. Amylase
Explanation: Amylase is found in saliva and pancreatic juice.
Question 20
The noble gas used in filling advertising neon signs is:
A. Argon
B. Helium
C. Neon
D. Radon
Answer: C. Neon
Explanation: Neon emits a bright red-orange glow when an electric current passes through it.
Question 21
Which of the following is a base?
A. NaCl
B. H2SO4
C. KOH
D. CH4
Answer: C. KOH
Explanation: Potassium hydroxide is an alkali (a soluble base).
Question 22
The heat change when one mole of a substance is formed from its elements is called enthalpy of:
A. Combustion
B. Neutralization
C. Formation
D. Solution
Answer: C. Formation
Explanation: Enthalpy of formation is the heat change when a compound is formed from its constituent elements in their standard states.
Question 23
What is the molar mass of NaOH? (Na=23, O=16, H=1)
Which of the following gases turns moist blue litmus paper red and then bleaches it?
A. Sulfur (IV) oxide
B. Chlorine
C. Ammonia
D. Hydrogen chloride
Answer: B. Chlorine
Explanation: Chlorine is acidic (turns blue litmus red) and is also a powerful bleaching agent.
Question 25
Elements in Group 1 of the periodic table are called:
A. Halogens
B. Noble gases
C. Alkali metals
D. Alkaline earth metals
Answer: C. Alkali metals
Explanation: Group 1 contains metals like Sodium and Potassium which are highly reactive.
Question 26
Which of the following is an electrolyte?
A. Sugar solution
B. Ethanol
C. Copper (II) tetraoxosulfate (VI) solution
D. Kerosene
Answer: C. Copper (II) tetraoxosulfate (VI) solution
Explanation: Electrolytes are substances that dissociate into ions in solution and conduct electricity.
Question 27
What type of reaction is: C2H4 + H2 -> C2H6?
A. Substitution
B. Addition
C. Elimination
D. Decomposition
Answer: B. Addition
Explanation: This is an addition reaction where an unsaturated compound becomes saturated.
Question 28
The Brownian motion provides evidence for the ______ nature of matter.
A. Wave
B. Continuous
C. Particulate
D. Stationary
Answer: C. Particulate
Explanation: The random motion of particles suggests that matter is made of tiny, moving particles.
Question 29
Which of the following elements is a halogen?
A. Sodium
B. Aluminum
C. Iodine
D. Neon
Answer: C. Iodine
Explanation: Halogens belong to Group 17 (VII) and include Fluorine, Chlorine, Bromine, and Iodine.
Question 30
The oxidation state of an element in its free uncombined state is:
A. +1
B. -1
C. 0
D. +2
Answer: C. 0
Explanation: By rule, the oxidation number of any pure element is zero.
Question 31
Temporary hardness in water is caused by the presence of:
A. Calcium trioxocarbonate (IV)
B. Calcium hydrogen trioxocarbonate (IV)
C. Magnesium tetraoxosulfate (VI)
D. Sodium chloride
Answer: B. Calcium hydrogen trioxocarbonate (IV)
Explanation: This compound decomposes upon boiling, which removes the hardness.
Question 32
The IUPAC name for CH3COOH is:
A. Methanoic acid
B. Ethanoic acid
C. Propanoic acid
D. Butanoic acid
Answer: B. Ethanoic acid
Explanation: A two-carbon chain acid is named ethanoic acid.
Question 33
Anhydrous copper (II) tetraoxosulfate (VI) is used as a test for water because it turns from white to ______ in the presence of water.
A. Green
B. Red
C. Blue
D. Black
Answer: C. Blue
Explanation: Hydrated copper (II) sulfate is blue.
Question 34
What is the percentage of Oxygen in CO2? (C=12, O=16)