Question
State and explain Avogadro’s law.
✓
Answer
i. In the year 1811, Avogadro made a distinction between atoms and molecules and thereby proposed Avogadro’s law. ii. Avogadro proposed that, “Equal volumes of all gases at the same temperature and pressure contain equal number of molecules”. e.g. Hydrogen gas combines with oxygen gas to produce water vapour as follows:
According to Avogadro’s law, if 1 volume contains n molecules, then 2n molecules of hydrogen combine with n molecules of oxygen to give 2n molecules of water, i.e., 2 molecules of hydrogen gas combine with 1 molecule of oxygen to give 2 molecules of water vapour as represented below:
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For the following reactions, write KC expressions and predict direction of the reactions based on the magnitude of their equilibrium constants.
i. $2 H _{2( g )}+ O _{2( g )} \rightleftharpoons 2 H _2 O _{( g )}, K _{ C }=2.4 \times 10^{47}$ at $500 K$
ii. $2 H _2 O _{( g )} \rightleftharpoons 2 H _{2( g )}+ O _{2( g )}, K _{ C }=4.2 \times 10^{-48}$ at $500 K$
→i. $2 H _{2( g )}+ O _{2( g )} \rightleftharpoons 2 H _2 O _{( g )}, K _{ C }=2.4 \times 10^{47}$ at $500 K$
ii. $2 H _2 O _{( g )} \rightleftharpoons 2 H _{2( g )}+ O _{2( g )}, K _{ C }=4.2 \times 10^{-48}$ at $500 K$
Explain: Liquefaction of $CO_2$ with the help of pressure vs volume isotherm.
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→Explain the terms: $i.$ Syngas $ii.$ Water-gas shift reaction.
→Match the following:
| Law | Statement | ||
| i. | Law of definite proportions | a. | When two elements A and B form more than one compounds, the masses of element B that combine with a given mass of A are always in the ratio of small whole numbers |
| ii. | Gay Lussac’s law | b. | Equal volumes of all gases at the same temperature and pressure contain equal number of molecules |
| iii. | Law of multiple proportions | c. | When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume, provided all gases are at same temperature and pressure |
| iv. | Avogadro’s law | d. | A given compound always contains exactly the same proportion of elements by weight |
Explain the following terms
(a) Mole fraction
(b) Molarity
(c) Molality
(a) Mole fraction
(b) Molarity
(c) Molality
Describe how London dispersion forces affect the boiling points of isomeric compounds like $n-$pentane and neopentane.
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Explain the variations in effective nuclear charge $i.$ Across a period $ii.$ Down a group
→Write the relationship between $K _{ C }$ and $K _{ p }$ for the following equilibria:
i. $H _{2( g )}+ Br _{2( g )} \rightleftharpoons 2 H B r _{( g )}$
ii. $\quad 2 NOBr _{( g )} \rightleftharpoons 2 NO _{( g )}+ B r _{2( g )}$
iii. $\quad ClF _{( g )}+ F _{2( g )} \rightleftharpoons ClF _{3( g )}$
→i. $H _{2( g )}+ Br _{2( g )} \rightleftharpoons 2 H B r _{( g )}$
ii. $\quad 2 NOBr _{( g )} \rightleftharpoons 2 NO _{( g )}+ B r _{2( g )}$
iii. $\quad ClF _{( g )}+ F _{2( g )} \rightleftharpoons ClF _{3( g )}$