Download CBSE MCQs for Class 7 Chemistry: Atomic Structure and Transformation of Matter
Review structured MCQ sets for Class 7 Chemistry Atomic Structure and Transformation of Matter. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.
Chapter-wise Objective Questions: Atomic Structure and Transformation of Matter
Access the complete set of multiple-choice questions for Atomic Structure and Transformation of Matter below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.
Multiple Choice Questions
(a) decomposition and combination
(b) double decomposition
(c) combination and displacement
(d) displacement and decomposition
Show Answer & Explanation
Answer: (a) decomposition and combination
Explanation:
1. Potassium nitrate decomposes on heating: \(\ce{2KNO3 -> 2KNO2 + O2}\).
2. The oxygen released combines with sulphur and carbon: \(\ce{S + O2 -> SO2}\) and \(\ce{C + O2 -> CO2}\).
3. So the changes are decomposition and combination.
Teacher's Note:
1. This mixture is gunpowder.
2. Split the process into the decomposition step and the burning steps.
(a) X, Y, Z, Cu
(b) Cu, Y, X, Z
(c) Cu, X, Z, Y
(d) Z, Cu, Y, X
Show Answer & Explanation
Answer: (d) Z, Cu, Y, X
Explanation:
1. X and Y both displace Cu, so each is more reactive than Cu.
2. Y cannot displace X from \(\ce{XSO4}\), so X is more reactive than Y.
3. Z cannot displace Cu, so Z is less reactive than Cu.
4. Ascending order: Z < Cu < Y < X, i.e. Z, Cu, Y, X.
Teacher's Note:
1. Ascending means least reactive first.
2. A metal that gives no reaction is less reactive.
(a) 1 : 3
(b) 3 : 1
(c) 3 : 4
(d) 3 : 2
Show Answer & Explanation
Answer: (a) 1 : 3
Explanation:
1. With valency 2 the sulphate is \(\ce{MSO4}\), with 4 oxygen atoms.
2. With valency 3 the sulphate is \(\ce{M2(SO4)3}\), with 12 oxygen atoms.
3. Ratio = 4 : 12 = 1 : 3.
Teacher's Note:
1. Find each sulphate by criss-cross.
2. Count oxygen inside the brackets as well.
(a) \(\ce{XH}\)
(b) \(\ce{XH3}\)
(c) \(\ce{XH4}\)
(d) \(\ce{XH2}\)
Show Answer & Explanation
Answer: (d) \(\ce{XH2}\)
Explanation:
1. Gaining two electrons gives \(\ce{X^2-}\), so the valency of X is 2.
2. With hydrogen (valency 1) the hydride is \(\ce{XH2}\).
Teacher's Note:
1. Valency equals electrons gained.
2. Swap valencies with hydrogen.
(a) X
(b) Z
(c) Y
(d) X and Y
Show Answer & Explanation
Answer: (b) Z
Explanation:
1. X has 2 electrons in shell 1 (He), Y has 8 in shell 2 (Ne, 2, 8) and Z has 6 in shell 3 (S, 2, 8, 6).
2. X and Y are noble gases with full shells, so they exist as single atoms.
3. Z (sulphur) is reactive and does not exist as single atoms: Z.
Teacher's Note:
1. Noble gases are monoatomic.
2. Sulphur forms molecules such as S8.
(a) 1 : 2
(b) 2 : 3
(c) 3 : 4
(d) 2 : 5
Show Answer & Explanation
Answer: (a) 1 : 2
Explanation:
1. First element: \(\ce{X^2-}\) has 8 electrons in L, so it is 2, 8; the atom is 2, 6, so Z = 8. Neutrons = 8, so A = 16.
2. Second element: \(\ce{Y^2-}\) has 8 electrons in M, so it is 2, 8, 8; the atom is 2, 8, 6, so Z = 16. Neutrons = 16, so A = 32.
3. Ratio = 16 : 32 = 1 : 2.
Teacher's Note:
1. Remove two electrons from the ion to get the atom.
2. A = protons + neutrons = 2Z here.
(a) 2 : 3
(b) 2 : 1
(c) 1 : 1
(d) 2 : 5
Show Answer & Explanation
Answer: (a) 2 : 3
Explanation:
1. The neutral atom has 13 electrons, arranged as 2, 8, 3.
2. K : M = 2 : 3.
3. So the ratio is 2 : 3.
Teacher's Note:
1. The neutral atom has the same number of electrons as protons.
2. Neutrons are not needed.
(a) 36,740
(b) 27,555
(c) 18,370
(d) 55,110
Show Answer & Explanation
Answer: (a) 36,740
Explanation:
1. The shells hold 2, 8, 8, 2 electrons, so there are 20 electrons and Z = 20.
2. Mass of 20 protons = 20 × 1837 = 36,740 times the mass of one electron.
Teacher's Note:
1. Work out the electrons from the ratio and the K shell value of 2.
2. Multiply Z by 1837.
(a) 2, 8, 2 and 2, 8, 6
(b) 2, 8 and 2, 8
(c) 2, 8 and 2, 8, 8
(d) 2, 8, 8 and 2, 8, 8
Show Answer & Explanation
Answer: (c) 2, 8 and 2, 8, 8
Explanation:
1. For X = 2, 8, x: 8 − 2 = 8 − x, so x = 2. X is 2, 8, 2.
2. The difference is 6, so Y has 6 valence electrons in M: 2, 8, 6.
3. X loses 2 electrons to form \(\ce{X^2+}\) (2, 8) and Y gains 2 to form \(\ce{Y^2-}\) (2, 8, 8).
4. So the answer is 2, 8 and 2, 8, 8.
Teacher's Note:
1. Find X first, then Y.
2. Stable ions have octet shells.
(a) silver
(b) silver chloride solution
(c) zinc
(d) gold
Show Answer & Explanation
Answer: (c) zinc
Explanation:
1. Only a metal more reactive than copper can displace it from copper sulphate.
2. Zinc is more reactive, so \(\ce{CuSO4 + Zn -> ZnSO4 + Cu}\).
3. The blue solution turns colourless, so the answer is zinc.
Teacher's Note:
1. Silver and gold are below copper in the series.
2. Blue colour comes from Cu²⁺ ions.
\(\ce{Cu(NO3)2.6H2O -> CuO + NO2 + H2O + O2}\)
(a) 2 : 3 : 1
(b) 1 : 2 : 6
(c) 1 : 1.5 : 1
(d) 3 : 2 : 1
Show Answer & Explanation
Answer: (b) 1 : 2 : 6
Explanation:
1. Balance: \(\ce{2Cu(NO3)2.6H2O -> 2CuO + 4NO2 + O2 + 12H2O}\).
2. Check oxygen: 24 on the left; 2 + 8 + 2 + 12 = 24 on the right.
3. The coefficients of CuO, \(\ce{NO2}\) and \(\ce{H2O}\) are 2, 4 and 12, so the ratio is 1 : 2 : 6.
Teacher's Note:
1. Balance Cu and N first, then H and O.
2. Divide by the common factor 2.
(a) Decomposition of HOCl on standing
(b) Formation of hydrogen chloride from their constituent elements
(c) Decomposition of limestone
(d) Both 1 and 2
Show Answer & Explanation
Answer: (a) Decomposition of HOCl on standing
Explanation:
1. Photolytic means decomposition by light.
2. HOCl breaks down in light: \(\ce{2HOCl -> 2HCl + O2}\).
3. Formation of HCl from elements is a combination, and limestone decomposes by heat. So the answer is (a).
Teacher's Note:
1. Photo means light.
2. Check which options are decompositions at all.
(a) dissolution of lime in water
(b) dissolution of carbon dioxide in water at high pressure
(c) dissolution of concentrated acid in water
(d) electrolysis of water
Show Answer & Explanation
Answer: (c) dissolution of concentrated acid in water
Explanation:
1. Dissolving lime and passing electricity through water make new substances, and carbon dioxide reacts with water to form carbonic acid.
2. Mixing a concentrated acid with water only dilutes it.
3. So only dissolution of concentrated acid in water is physical.
Teacher's Note:
1. Dilution leaves the acid unchanged.
2. Check for a new substance.
(a) calculation of the number of protons and neutrons
(b) identification of the atomic number and mass number of the given element
(c) placement of the electrons in shells around the nucleus according to the electronic configuration
(d) writing the electronic configuration of the atom
(e) protons and neutrons are shown in nucleus
(a) baedc
(b) bacde
(c) abced
(d) ecbad
Show Answer & Explanation
Answer: (a) baedc
Explanation:
1. Identify Z and A (b).
2. Calculate protons and neutrons (a).
3. Show them in the nucleus (e).
4. Write the electronic configuration (d).
5. Place the electrons in the shells (c).
6. So the sequence is b, a, e, d, c.
Teacher's Note:
1. Nucleus first, then the shells.
2. You need Z and A before anything else.
(b) \(\ce{HBr + NaOH -> NaBr + H2O}\)
(c) \(\ce{2NaBr + Cl2 -> 2NaCl + Br2}\)
(d) \(\ce{2NaCl -> 2Na + Cl2}\)
Arrange the above reactions in order as double displacement reaction, combination reaction, decomposition reaction and displacement reaction.
(a) badc
(b) bdac
(c) bacd
(d) abdc
Show Answer & Explanation
Answer: (a) badc
Explanation:
1. Double displacement: (b), since two compounds exchange radicals.
2. Combination: (a), two elements form one compound.
3. Decomposition: (d), one compound gives two elements.
4. Displacement: (c), chlorine displaces bromine.
5. So the order is b, a, d, c.
Teacher's Note:
1. Identify each reaction type first.
2. Then write them in the order asked.
Potassium permanganate oxidizes oxalic acid in an acidic medium as per the above chemical reaction. Identify the coefficient of \(\ce{H2SO4}\) in the above equation.
(a) 3
(b) 4
(c) 5
(d) 2
Show Answer & Explanation
Answer: (a) 3
Explanation:
1. Sulphur on the right: 1 in \(\ce{K2SO4}\) and 2 in \(\ce{2MnSO4}\), total 3.
2. So \(\ce{H2SO4}\) must have the coefficient 3.
3. Hydrogen check: 6 + 10 = 16 on the left and 16 on the right.
Teacher's Note:
1. Count sulphur on the product side.
2. Verify with hydrogen.
(a) \(\ce{M2(SO4)3}\)
(b) \(\ce{MSO4}\)
(c) \(\ce{M2SO4}\)
(d) \(\ce{MSO3}\)
Show Answer & Explanation
Answer: (a) \(\ce{M2(SO4)3}\)
Explanation:
1. Sulphate is \(\ce{SO4^2-}\).
2. Criss-cross gives \(\ce{M2(SO4)3}\).
Teacher's Note:
1. Swap 3 and 2.
2. Keep the radical in brackets.
Column A: (A) Chlorine (B) Scandium (C) Manganese (D) Beryllium
Column B: (a) 2, 2 (b) 2, 8, 7 (c) 2, 8, 9, 2 (d) 2, 8, 13, 2
(a) A → c, B → d, C → a, D → b
(b) A → d, B → a, C → b, D → c
(c) A → b, B → c, C → d, D → a
(d) A → d, B → a, C → c, D → b
Show Answer & Explanation
Answer: (c) A → b, B → c, C → d, D → a
Explanation:
1. Chlorine (Z = 17) is 2, 8, 7: A → b.
2. Scandium (Z = 21) is 2, 8, 9, 2: B → c.
3. Manganese (Z = 25) is 2, 8, 13, 2: C → d.
4. Beryllium (Z = 4) is 2, 2: D → a.
5. So the answer is A → b, B → c, C → d, D → a.
Teacher's Note:
1. Use the atomic numbers of the elements.
2. The sums must match Z.
Assertion (A): Mass number of carbon is 12.
Reason (R): Carbon possesses equal number of all three fundamental particles.
(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.
Show Answer & Explanation
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Explanation:
1. A is true: carbon has 6 protons and 6 neutrons, so its mass number is 12.
2. R is true: it has 6 protons, 6 neutrons and 6 electrons.
3. But equal numbers alone do not fix the mass number at 12 (it could be any number), so R does not explain A.
4. So both are true but R is not the correct explanation: (b).
Teacher's Note:
1. The mass number depends on the actual count of protons and neutrons.
2. An explanation must lead directly to the statement.
(a) 18
(b) 19
(c) 16
(d) 17
Show Answer & Explanation
Answer: (b) 19
Explanation:
1. Equal numbers in L and M means 8 and 8, so the configuration starts 2, 8, 8.
2. Argon (18) has 2, 8, 8 but is a noble gas, not a metal.
3. Z = 19 is 2, 8, 8, 1, which is potassium, a metal: 19.
Teacher's Note:
1. Write out the configurations.
2. 16 and 17 have fewer than 8 in M.
(a) 2, 8, 1
(b) 2, 7
(c) 2, 8
(d) 2, 8, 8
Show Answer & Explanation
Answer: (b) 2, 7
Explanation:
1. The atom has 9 protons, so 9 electrons.
2. They are arranged 2, 7.
3. So the configuration is 2, 7.
Teacher's Note:
1. Atom and ion differ by the extra electron.
2. Neutrons do not change the configuration.
Assertion (A): Copper exhibits variable valency.
Reason (R): Copper loses two electrons from its valence shell and it can also lose one more electron from the second last shell.
(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.
Show Answer & Explanation
Answer: (c) A is true, but R is false.
Explanation:
1. A is true: copper forms \(\ce{Cu+}\) and \(\ce{Cu^2+}\).
2. R is false: copper has only one electron in its valence shell, so it loses one electron from the valence shell and, to form \(\ce{Cu^2+}\), one more from the second last shell.
3. So A is true and R is false: (c).
Teacher's Note:
1. Copper is 2, 8, 18, 1.
2. Check the number of valence electrons before accepting R.
(a) 2, 8, 5 and 2, 8, 4
(b) 2, 8, 8 and 2, 8, 6
(c) 2, 8, 8 and 2, 6, 6
(d) 2, 8, 6 and 2, 8, 4
Show Answer & Explanation
Answer: (b) 2, 8, 8 and 2, 8, 6
Explanation:
1. X is stable with M as valence shell: 2, 8, 8, difference 6.
2. For Y: (8 − 2) : (x − 2) = 3 : 2, so x = 6.
3. So X is 2, 8, 8 and Y is 2, 8, 6.
Teacher's Note:
1. Use the ratio to find the unknown.
2. Y has the M shell with 6 electrons.
(a) passing of steam over a red hot coke
(b) change in the colour of dil nitric acid upon long standing
(c) absorption of moisture by \(\ce{P2O5}\)
(d) absorption of moisture by \(\ce{CaCl2}\)
Show Answer & Explanation
Answer: (d) absorption of moisture by \(\ce{CaCl2}\)
Explanation:
1. Steam with red hot coke and the colour change of nitric acid make new substances, and \(\ce{P2O5}\) reacts with water to form an acid.
2. Calcium chloride only absorbs water without any reaction, so it is not a chemical change.
Teacher's Note:
1. Look for a new substance.
2. Deliquescence is physical.
(a) A
(b) B
(c) C
(d) both A and B
Show Answer & Explanation
Answer: (c) C
Explanation:
1. A is 2, 8 and B is 2, 8, 8: both have an octet and are inactive.
2. C is 2, 6 and needs 2 more electrons, so it is reactive: C.
Teacher's Note:
1. Write the configurations.
2. Octet means stable.
(a) 1 : 2
(b) 3 : 5
(c) 12 : 19
(d) 2 : 3
Show Answer & Explanation
Answer: (b) 3 : 5
Explanation:
1. X: 12 protons + 12 neutrons = 24. \(\ce{X^2+}\) has 10 electrons.
2. Y: \(\ce{Y^2+}\) has 18 electrons, so Y has 20 protons. Neutrons of Y = 2 × 10 = 20, so A = 40.
3. Ratio = 24 : 40 = 3 : 5.
Teacher's Note:
1. Dipositive means two electrons lost.
2. Compute each mass number separately.
(a) 4
(b) 3
(c) 1
(d) 2
Show Answer & Explanation
Answer: (d) 2
Explanation:
1. Chloride has valency 1 and two are present.
2. So the metal has valency 2.
Teacher's Note:
1. The Cl subscript gives the metal's valency.
2. Test with criss-cross.
(a) physical state only
(b) physical state as well as chemical composition
(c) colour only
(d) both colour and volume only
Show Answer & Explanation
Answer: (b) physical state as well as chemical composition
Explanation:
1. Solid \(\ce{NH4Cl}\) sublimes (a physical change).
2. It also decomposes into \(\ce{NH3}\) and \(\ce{HCl}\) (a chemical change).
3. So the answer is physical state as well as chemical composition.
Teacher's Note:
1. Two changes occur together.
2. Decomposition changes composition.
(a) Protons and neutrons are shown in the nucleus.
(b) Writing the electronic configuration of the atom.
(c) Arrange the electrons in shells around the nucleus following the electronic configuration.
(d) Calculation of the number of protons and neutrons.
(e) Identification of the atomic number and mass number of the atom.
(a) edcba
(b) edabc
(c) abcde
(d) cabde
Show Answer & Explanation
Answer: (b) edabc
Explanation:
1. Identify Z = 20 and A = 40 (e).
2. Calculate 20 protons and 20 neutrons (d).
3. Show them in the nucleus (a).
4. Write the configuration 2, 8, 8, 2 (b).
5. Place the electrons in the shells (c).
6. So the order is e, d, a, b, c.
Teacher's Note:
1. Start with the data, end with the electrons.
2. The nucleus is drawn before the shells.
(a) displacement reaction
(b) combination reaction
(c) double displacement
(d) decomposition reaction
Follow this sequence to arrange the following reactions:
(a) \(\ce{A + B -> AB}\).
(b) \(\ce{AB -> A + B}\)
(c) \(\ce{AB + C -> CB + A}\)
(d) \(\ce{AC + BD -> AD + BC}\)
(a) cadb
(b) bacd
(c) bdac
(d) acbd
Show Answer & Explanation
Answer: (a) cadb
Explanation:
1. Displacement: \(\ce{AB + C -> CB + A}\) (c).
2. Combination: \(\ce{A + B -> AB}\) (a).
3. Double displacement: \(\ce{AC + BD -> AD + BC}\) (d).
4. Decomposition: \(\ce{AB -> A + B}\) (b).
5. So the order is c, a, d, b.
Teacher's Note:
1. Label each reaction first.
2. Then follow the order of the types given.
\(\ce{2Cu(NO3)2.6H2O -> CuO + NO2 + 12H2O + O2}\)
(a) 3, 4
(b) 2, 4
(c) 4, 5
(d) 2, 3
Show Answer & Explanation
Answer: (b) 2, 4
Explanation:
1. Copper: 2 Cu on the left, so CuO has coefficient 2.
2. Nitrogen: 4 N on the left, so \(\ce{NO2}\) has coefficient 4.
3. Oxygen check: 24 on the left and 2 + 8 + 12 + 2 = 24 on the right.
4. So the coefficients are 2 and 4.
Teacher's Note:
1. Balance metal and nitrogen first.
2. Check oxygen last.
(a) \(\ce{M2(PO4)3}\)
(b) \(\ce{MHPO4}\)
(c) \(\ce{M(H2PO4)2}\)
(d) \(\ce{M2HPO4}\)
Show Answer & Explanation
Answer: (c) \(\ce{M(H2PO4)2}\)
Explanation:
1. Dihydrogen phosphate is \(\ce{H2PO4-}\).
2. Criss-cross with \(\ce{M^2+}\) gives \(\ce{M(H2PO4)2}\).
Teacher's Note:
1. Use brackets for a repeated radical.
2. Do not confuse it with hydrogen phosphate.
Column A: (A) Neon (B) Oxygen (C) Potassium (D) Boron (E) Silicon
Column B: (a) 4 (b) 3 (c) 2 (d) 1 (e) 0
(a) A → b, B → c, C → d, D → e, E → a
(b) A → b, B → c, C → a, D → e, E → d
(c) A → e, B → d, C → a, D → b, E → c
(d) A → e, B → c, C → d, D → b, E → a
Show Answer & Explanation
Answer: (d) A → e, B → c, C → d, D → b, E → a
Explanation:
1. Neon (2, 8) is inactive: valency 0, A → e.
2. Oxygen (2, 6) gains 2: valency 2, B → c.
3. Potassium (2, 8, 8, 1) loses 1: valency 1, C → d.
4. Boron (2, 3) loses 3: valency 3, D → b.
5. Silicon (2, 8, 4) has valency 4, E → a.
6. So the answer is option (d).
Teacher's Note:
1. Write the configuration of each element.
2. Valency is the electrons lost, gained or zero.
Assertion (A): The total mass of the protons of a boron atom is 6185 times the total mass of electrons.
Reason (R): Mass of one proton is 1837 times the mass of electron.
(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.
Show Answer & Explanation
Answer: (d) A is false, but R is true.
Explanation:
1. R is true: a proton is about 1837 times as heavy as an electron.
2. Boron has 5 protons, so their total mass is 5 × 1837 = 9185 times the mass of one electron (and 1837 times the mass of its 5 electrons). The value 6185 in A is wrong.
3. So A is false and R is true: (d).
Teacher's Note:
1. Multiply the number of protons by 1837 to compare with one electron.
2. Check the arithmetic in A.
(a) 20 and 13
(b) 13 and 20
(c) 17 and 20
(d) 20 and 14
Show Answer & Explanation
Answer: (d) 20 and 14
Explanation:
1. Neutrons = A − Z.
2. 40 − 20 = 20 and 27 − 13 = 14.
3. So the numbers are 20 and 14.
Teacher's Note:
1. Subtract the atomic number from the mass number.
2. Do it for each element.
(a) 2
(b) 1
(c) 3
(d) 5
Show Answer & Explanation
Answer: (c) 3
Explanation:
1. The neutral atom has 13 electrons: 2, 8, 3.
2. So the M shell has 3 electrons.
Teacher's Note:
1. Neutral atom: electrons = protons.
2. Fill K, L, then M.
Assertion (A): Sodium forms a monovalent ion.
Reason (R): Sodium loses only one electron from the second last shell.
(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.
Show Answer & Explanation
Answer: (c) A is true, but R is false.
Explanation:
1. A is true: sodium (2, 8, 1) loses one electron and forms \(\ce{Na+}\).
2. R is false: the electron is lost from the outermost (valence) shell, not the second last shell.
3. So A is true and R is false: (c).
Teacher's Note:
1. Sodium has one valence electron.
2. Check which shell the electron comes from.
(a) 2, 8, 2 and 2, 8, 6
(b) 2, 8 and 2, 8
(c) 2, 8 and 2, 8, 8
(d) 2, 8, 8 and 2, 8, 8
Show Answer & Explanation
Answer: (c) 2, 8 and 2, 8, 8
Explanation:
1. For X: 8 − 2 = 8 − x gives x = 2, so X is 2, 8, 2. The difference is 6, so Y is 2, 8, 6.
2. X loses 2 electrons: \(\ce{X^2+}\) is 2, 8.
3. Y gains 2 electrons: \(\ce{Y^2-}\) is 2, 8, 8.
4. So the answer is 2, 8 and 2, 8, 8.
Teacher's Note:
1. Find the elements first.
2. Metal loses, nonmetal gains.
(a) formation of clouds
(b) formation of rust
(c) manufacture of milk powder from milk
(d) formation of black coating on the walls of a tube light
Show Answer & Explanation
Answer: (b) formation of rust
Explanation:
1. Clouds, milk powder and the black coating on a tube light involve no new substance.
2. Rust is a new compound, so formation of rust is a chemical change.
Teacher's Note:
1. Rusting makes hydrated ferric oxide.
2. The others are physical.
(a) X
(b) Z
(c) Y
(d) X and Y
Show Answer & Explanation
Answer: (b) Z
Explanation:
1. X is helium and Y is neon: noble gases that exist as single atoms.
2. Z is sulphur (2, 8, 6), a reactive element that exists as molecules: Z.
Teacher's Note:
1. Noble gases are monoatomic.
2. Reactive elements form molecules.
(a) 1 : 2
(b) 2 : 3
(c) 3 : 4
(d) 2 : 5
Show Answer & Explanation
Answer: (a) 1 : 2
Explanation:
1. X: \(\ce{X^2-}\) is 2, 8, so X is 2, 6 with Z = 8 and A = 16.
2. Y: \(\ce{Y^2-}\) is 2, 8, 8, so Y is 2, 8, 6 with Z = 16 and A = 32.
3. Ratio = 16 : 32 = 1 : 2.
Teacher's Note:
1. A = 2Z when neutrons equal protons.
2. Remove two electrons from the ion to get the atom.
(a) 3
(b) 5
(c) 6
(d) 4
Show Answer & Explanation
Answer: (b) 5
Explanation:
1. In \(\ce{X2O5}\) the total negative charge is 5 × 2 = 10 for two X atoms.
2. So each X has valency 5.
3. Criss-cross check: \(\ce{X^5+}\) with \(\ce{O^2-}\) gives \(\ce{X2O5}\).
Teacher's Note:
1. Swap the subscripts to read the valency.
2. X has 5 and oxygen has 2.
Free study material for Science
Multiple Choice Questions (MCQs) for Class 7 Chemistry Atomic Structure and Transformation of Matter
Class 7 Chemistry Atomic Structure and Transformation of Matter Objective Test Questions
Test your conceptual understanding of Atomic Structure and Transformation of Matter with these targeted multiple-choice questions. Designed in alignment with the latest CBSE curriculum for Class 7 Chemistry, these problem sets build accuracy and prepare students for objective exams.
NCERT-Aligned Objective Questions and Solutions
Each question includes structured solution keys mapped directly to standard CBSE textbooks, helping students evaluate their reasoning and correct mistakes early in their revision.
Next Steps in Your Exam Preparation
Wrap up your chapter revision by testing your knowledge against standard question formats. Everything on our platform is provided free of charge.
FAQs
You can get most exhaustive CBSE Class 7 Science Advanced Chemistry Atomic Structure and Transformation of Matter MCQs Set 02 for free on StudiesToday.com. These MCQs for Class 7 Chemistry are updated for the 2026-27 academic session as per CBSE examination standards.
Yes, our CBSE Class 7 Science Advanced Chemistry Atomic Structure and Transformation of Matter MCQs Set 02 include the latest type of questions, such as Assertion-Reasoning and Case-based MCQs. 50% of the CBSE paper is now competency-based.
By solving our CBSE Class 7 Science Advanced Chemistry Atomic Structure and Transformation of Matter MCQs Set 02, Class 7 students can improve their accuracy and speed which is important as objective questions provide a chance to secure 100% marks in the Chemistry.
Yes, Chemistry MCQs for Class 7 have answer key and brief explanations to help students understand logic behind the correct option as its important for 2026 competency-focused CBSE exams.
Yes, you can also access online interactive tests for CBSE Class 7 Science Advanced Chemistry Atomic Structure and Transformation of Matter MCQs Set 02 on StudiesToday.com as they provide instant answers and score to help you track your progress in Chemistry.