ACME ACADEMY

WEEKLY EVALUATION TEST

Subject: Science
Time Limit: 20 Mins
Max Marks: 20 Marks
Student Name:
Roll Number:
Class / Sec:
Date:

GENERAL INSTRUCTIONS:

  1. All questions are compulsory. Carefully read all instructions before starting.
  2. The question paper contains 20 questions.
  3. There is no negative marking for incorrect answers.
  4. Use of mobile phones, smartwatches, or calculators is strictly prohibited during the exam.
1. Which scientific law states that matter can neither be created nor destroyed in a chemical reaction?
[1 Mark]
(A) Law of Definite Proportions
(B) Law of Conservation of Mass
(C) Law of Multiple Proportions
(D) Law of Conservation of Energy
2. If 100 g of calcium carbonate is heated and completely decomposes to produce 56 g of calcium oxide and an unknown mass of carbon dioxide gas, what must the mass of the carbon dioxide be?
[1 Mark]
(A) 156 g
(B) 100 g
(C) 44 g
(D) 56 g
3. Water obtained from a river, a well, or an ocean, when purified, will always contain hydrogen and oxygen in a mass ratio of 1:8. This observation directly supports which law?
[1 Mark]
(A) Law of Conservation of Mass
(B) Law of Constant Proportions
(C) Law of Gravity
(D) Dalton's Postulate of Indivisibility
4. According to Dalton’s Atomic Theory, why do compounds have a fixed composition by mass?
[1 Mark]
(A) Because atoms are constantly changing their masses.
(B) Because atoms of different elements combine in the ratio of simple whole numbers to form compounds.
(C) Because all atoms of all elements are exactly identical.
(D) Because chemical reactions create new atoms in fixed amounts.
5. How is a 'molecule' scientifically defined?
[1 Mark]
(A) The smallest indivisible part of an element.
(B) An electrically neutral entity consisting of more than one atom, capable of independent existence, showing all properties of that substance.
(C) A positively charged particle found only in metals.
(D) A mixture of two different elements combined in any ratio.
6. When two chlorine atoms combine to form a Cl2 molecule, they share one electron each to achieve a stable octet. What specific type of chemical bond is this?
[1 Mark]
(A) Single Ionic bond
(B) Double Covalent bond
(C) Single Covalent bond
(D) Metallic bond
7. In the formation of an oxygen molecule (O2), each oxygen atom has 6 valence electrons and needs 2 more to complete its octet. How do they bond?
[1 Mark]
(A) By transferring two electrons from one atom to another.
(B) By sharing two pairs of electrons, forming a double covalent bond.
(C) By sharing one pair of electrons, forming a single covalent bond.
(D) By losing two electrons each.
8. Sodium (atomic number 11) has 1 valence electron, while Chlorine (atomic number 17) has 7 valence electrons. How is a stable bond formed between them?
[1 Mark]
(A) Sodium shares one electron with chlorine.
(B) Sodium transfers its 1 valence electron to chlorine, forming a positive sodium cation and a negative chloride anion, which are held by electrostatic forces.
(C) Chlorine transfers 7 electrons to sodium.
(D) Both atoms lose all their valence electrons.
9. Covalent compounds are generally formed by:
[1 Mark]
(A) The transfer of electrons between two metals.
(B) The sharing of electrons between non-metals.
(C) The strong electrostatic attraction between cations and anions.
(D) The random collision of protons.
10. Using the criss-cross method for valencies, what is the correct chemical formula for aluminium oxide? (Given: Al valency = 3, O valency = 2)
[1 Mark]
(A) AlO
(B) Al3O2
(C) Al2O3
(D) AlO3
11. What is the correct chemical formula for magnesium hydroxide?
[1 Mark]
(A) MgOH
(B) Mg2OH
(C) Mg(OH)2
(D) Mg2(OH)3
12. Which of the following is a characteristic property of ionic compounds like sodium chloride?
[1 Mark]
(A) They have very low melting and boiling points.
(B) They consist of discrete, independent molecules.
(C) They are generally soluble in organic solvents like petrol.
(D) They conduct electricity when dissolved in water but not in the solid state.
13. Assertion (A): Covalent compounds like camphor and naphthalene do not conduct electricity in an aqueous solution. Reason (R): Covalent compounds do not provide free ions in a solution.
[1 Mark]
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
14. Calculate the molecular mass of water (H2O). (Given atomic masses: H = 1 u, O = 16 u)
[1 Mark]
(A) 17 u
(B) 18 u
(C) 33 u
(D) 34 u
15. Why do we calculate 'formula unit mass' instead of 'molecular mass' for a substance like Calcium Chloride (CaCl2)?
[1 Mark]
(A) Because calcium is a gas.
(B) Because ionic compounds do not exist as discrete molecules, but rather as 3-D crystal lattices of repeating ions.
(C) Because its mass is constantly changing.
(D) Because the covalent bonds are too weak.
16. Calculate the formula unit mass of Sodium Oxide (Na2O). (Given atomic masses: Na = 23 u, O = 16 u)
[1 Mark]
(A) 39 u
(B) 62 u
(C) 46 u
(D) 54 u
17. In the compound PCl3, how would it be correctly named according to the prefix system for covalent compounds?
[1 Mark]
(A) Phosphorus chloride
(B) Monophosphorus trichloride
(C) Phosphorus trichloride
(D) Triphosphorus monochloride
18. If 12 g of carbon combines exactly with 32 g of oxygen to form 44 g of carbon dioxide, what mass of carbon dioxide will be produced if 3 g of carbon is burnt in an unlimited supply of oxygen?
[1 Mark]
(A) 3 g
(B) 11 g
(C) 44 g
(D) 12 g
19. A polyatomic ion is:
[1 Mark]
(A) An ion formed by the combination of atoms of two or more elements acting as a single charged unit.
(B) An atom that has lost all its protons.
(C) A single metal atom with a +4 charge.
(D) A molecule that has no charge.
20. When an atom 'A' with 2 valence electrons combines with an atom 'B' with 6 valence electrons, what is the most likely outcome?
[1 Mark]
(A) Atom A shares 2 electrons with Atom B to form a covalent bond.
(B) Atom A transfers 2 electrons to Atom B, forming an ionic compound consisting of A2+ and B2- ions.
(C) They do not react as they both repel each other.
(D) Atom B transfers 6 electrons to Atom A.
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