2 What should you do before using any chemical in the lab? A Smell it B Read the label and hazard signs C Taste it D Mix it with another chemical
3 The mass number (A) of an atom is equal to the sum of: A protons and electrons B protons and neutrons C neutrons and electrons D protons only
4 A closed system is necessary for dynamic equilibrium because: A reactants cannot be added B products cannot be removed C matter cannot enter or leave D temperature remains constant
6 Percentage error is calculated as: A (Error / True value) × 100 B (True value / Error) × 100 C (Error × True value) / 100 D Error + True value
7 Which indicator turns red in acidic solution and yellow in basic solution? A Litmus B Phenolphthalein C Methyl orange D Universal indicator
8 Cracking of hydrocarbons is used to: A Combine small molecules B Break large molecules into smaller ones C Remove hydrogen D Add halogens
9 How many moles are present in 36 g of water (H2O)? (Molar mass of H2O = 18 g/mol) A 2 moles B 1 mole C 0.5 mole D 4 moles
10 Which property generally decreases as you move from left to right across a period in the periodic table? A Atomic size B Ionisation energy C Electronegativity D Non-metallic character
11 Acid rain is mainly caused by the presence of which gases in the atmosphere? A CO2 and O2 B SO2 and NOx C CH4 and H2 D N2 and O2
12 Which SI base unit is used to measure the amount of a substance? A Kilogram (kg) B Mole (mol) C Kelvin (K) D Ampere (A)
13 Which gas is the most abundant in the Earth's atmosphere? A Oxygen B Nitrogen C Carbon dioxide D Argon
14 Hydrogen bonding occurs when hydrogen is bonded to: A Carbon, nitrogen, or oxygen B Fluorine, oxygen, or nitrogen C Chlorine, bromine, or iodine D Any metal
16 The bond formed between two chlorine atoms in Cl2 molecule is: A Ionic B Covalent C Coordinate covalent D Metallic
17 Which statement about a reversible reaction is correct? A It can proceed in both forward and backward directions. B It goes only to completion. C It never reaches equilibrium. D It uses a single arrow.
18 Which Group 1 element reacts most vigorously with water? A Lithium B Sodium C Potassium D Hydrogen
19 Acid rain is mainly caused by the reaction of water vapour with: A Sulphur dioxide and nitrogen oxides B Carbon dioxide and oxygen C Nitrogen and argon D Oxygen and ozone
20 The branch of chemistry that deals with the study of radioactive substances is: A Polymer chemistry B Nuclear chemistry C Geochemistry D Biochemistry
21 Which human activity is a major source of carbon dioxide emissions? A Planting trees B Burning fossil fuels C Using solar energy D Recycling waste
22 Which is a limitation of the Arrhenius concept? A It explains acid-base behavior in water only B It explains all acid-base reactions in gases C It defines acids as proton donors D It defines bases as electron pair donors
23 According to collision theory, a reaction occurs when reactant molecules collide with sufficient energy and proper ____. A orientation B mass C volume D density
24 Alkenes are more reactive than alkanes because they contain: A A double bond B Only single bonds C A triple bond D An aromatic ring
25 Which of the following is a correct step to determine the empirical formula? A Divide the moles of each element by the smallest number of moles B Multiply the moles of each element by the smallest number of moles C Add the moles of all elements D Ignore the smallest number of moles