# 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 |
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Match the following:

 COLUMN I COLUMN II A. 88 g of CO2 1. 0.25 mol B. 6.022×1023 molecules of H2O 2. 2 mol C. 5.6 L of O2 at 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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Match the following physical quantities with units.

 Physical quantity Unit A. Molarity 1. mol kg–1 B. Molality 2. mol L–1 C. Pressure 3. Candela D. Luminous intensity 4. Pascal

Codes:

 A B C D 1. 1 4 2 3 2. 2 1 4 3 3. 1 4 3 2 4. 4 1 3 2
Subtopic:  Introduction |
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 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.

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

1. $2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to 2\mathrm{MgO}\left(\mathrm{s}\right)$

2. ${\mathrm{C}}_{3}{\mathrm{H}}_{8}\left(\mathrm{g}\right)+{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to {\mathrm{CO}}_{2}\left(\mathrm{g}\right)+{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{g}\right)$

3. ${\mathrm{P}}_{4}\left(\mathrm{s}\right)+5{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to {\mathrm{P}}_{4}{\mathrm{O}}_{10}\left(\mathrm{s}\right)$

4. ${\mathrm{CH}}_{4}\left(\mathrm{g}\right)+2{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to {\mathrm{CO}}_{2}\left(\mathrm{g}\right)+2{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{g}\right)$

Subtopic:  Introduction |
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The incorrect statement among the following is:

 1 A molecule of a compound has atoms of different elements. 2 A compound cannot be separated into its constituent elements by the physical method of separation. 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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If the density of the solution is 3.12 g ml-1, then what will be the mass of the 1.5 ml solution in two significant figures?

 1 $$4.4~\mathrm{g}$$ 2 $$4680 \times 10^{3} ~\mathrm{g}$$ 3 $$4.7~\mathrm{g}$$ 4 $$46.80~\mathrm{g}$$
Subtopic:  Introduction |
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