Identify the reaction that does not obey the law of conservation of mass from the provided options:

1. $2 Mg (s) + O_{2} (g) \to 2 MgO (s)$

2. $C_{3} H_{8} (g) + O_{2} (g) \to {CO}_{2} (g) + H_{2} O (g)$

3. $P_{4} (s) + 5 O_{2} (g) \to P_{4} O_{10} (s)$

4. ${CH}_{4} (g) + 2 O_{2} (g) \to {CO}_{2} (g) + 2 H_{2} O (g)$

Subtopic: Introduction |

84%

Level 1: 80%+

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Q209:

Which of the following statement indicates that the law of multiple proportions is being followed?

1.	A sample of carbon dioxide taken from any source will always have carbon and oxygen in the ratio of 1:2.
2.	Carbon forms two oxides namely, CO₂ and CO, where masses of oxygen that combine with a fixed mass of carbon are in the simple ratio of 2:1.
3.	When magnesium burns in oxygen, the amount of magnesium used for the reaction is equal to the amount of magnesium formed in magnesium oxide.
4.	At constant temperature and pressure, 200 mL of hydrogen will combine with 100 mL of oxygen to produce 200 mL of water vapour.

Subtopic: Introduction |

80%

Level 1: 80%+

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Q210:

Match the following:

	Column-I		Column-II
A.	88 g of CO₂	1.	0.25 mol
B.	6.022×10²³molecules of H₂O	2.	2 mol
C.	5.6 L of O₂at STP	3.	3 mol
D.	96 g of O₂	4.	1 mol

Codes:

	A	B	C	D
1.	2	4	1	3
2.	1	2	3	4
3.	1	4	3	2
4.	4	1	3	2

Subtopic: Moles, Atoms & Electrons |

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Level 1: 80%+

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Q211:

Match the following physical quantities with units.

	Physical quantity		Unit
A.	Molarity	(i).	mol kg^–1
B.	Molality	(ii).	mol L^–1
C.	Pressure	(iii).	Candella
D.	Luminous intensity	(iv).	Pascal

Codes:

	A	B	C	D
1.	(i)	(iv)	(ii)	(iii)
2.	(ii)	(i)	(iv)	(iii)
3.	(i)	(iv)	(iii)	(ii)
4.	(iv)	(i)	(iii)	(ii)

Subtopic: Introduction |

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Level 1: 80%+

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Q212:

Consider the given two statements:

Assertion (A):	The empirical mass of ethene is half of its molecular mass.
Reason (R):	The empirical formula represents the simplest whole-number ratio of the various atoms present in a compound.

Select the correct option:

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	(A) is False but (R) is True.

Subtopic: Empirical & Molecular Formula |

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Level 2: 60%+

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Q213:

Given below are two statements:

Assertion (A):	One atomic mass unit is defined as one-twelfth of the mass of one carbon-12 atom.
Reason (R):	The carbon-12 isotope is the most abundant isotope of carbon and has been chosen as the standard.

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	(A) is False but (R) is True.

Subtopic: Moles, Atoms & Electrons |

Level 3: 35%-60%

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Q214:

Assertion (A):	The significant figure for 0.200 is 3, whereas the significant figure for 200 is 1.
Reason (R):	Zero at the end or right of a number is significant, provided it is not on the right side of the decimal point.

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	(A) is False but (R) is True.

Subtopic: Introduction |

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Level 3: 35%-60%

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Q215:

Assertion (A):	The combustion of 16 g of methane gives 18 g of water.
Reason (R):	In the combustion of methane, water is one of the products.

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	(A) is False but (R) is True.

Subtopic: Moles, Atoms & Electrons |

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Level 2: 60%+

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Q207:

Which of the following statements about the reaction given below is correct?

$4 Fe (s) + 3 O_{2} (g) \to 2 {Fe}_{2} O_{3} (g)$

1.	Total mass of iron and oxygen in reactants = total mass of iron and oxygen in product therefore it follows the law of conservation of mass
2.	Total mass of reactants = total mass of product, therefore, the law of multiple proportions is followed
3.	The amount of Fe₂O₃ can be increased by taking any one of the reactants (iron or oxygen) in excess.
4.	The amount of Fe₂O₃ produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess.

Subtopic: Limiting Reagent |

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Level 2: 60%+

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Q206:

The incorrect statement among the following is:

1.	A molecule of a compound contains atoms from various elements.
2.	A compound cannot be broken down into its constituent elements using physical separation techniques.
3.	A compound retains the physical properties of its constituent elements.
4.	The ratio of atoms of different elements in a compound is fixed.

Subtopic: Introduction |

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Identify the reaction that does not obey the law of conservation of mass from the provided options: 1. 2Mg(s)+O2(g)→2MgO(s) 2. C3H8(g)+O2(g)→CO2(g)+H2O(g) 3. P4(s)+5O2(g)→P4O10(s) 4. CH4(g)+2O2(g)→CO2(g)+2H2O(g)

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