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Published on: 30/12/2018
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1.
Why are alkali metals always univalent? Which alkali metal ion forms largest hydrated ion in aqueous solution?
2.
Identify the oxidant and reductant in the following redox reaction:
2K2MnO4 + Cl2 \(\rightarrow\) 2kcl + 2KMnO4
3.
What do you understand by 'Representative elements'? Name the groups whose elements are called representative elements.
4.
Calculate the number of moles in each of the following.
44.8 litres of sulphur dioxide at N.T.P.
5.
Write down the formula of the first four members of each homologous series beginning with the following compounds.
(i) \({ CH }_{ 2 }={ CH }_{ 2 }\)
(ii) \(HCOOH\)
(iii) \({ CH }_{ 3 }CO{ CH }_{ 3 }\)
(iv) \({ CH }_{ 3 }OH\)
(v) \(HC\equiv CH\)
6.
10 g of argon is compressed isothermally and reversibly at a temperature of 27oC from 10 L to 5 L. Calculate q, W, \(\Delta\)U and \(\Delta\)H for this process R = 2.0 cal K -1 mol-1, log2 = 0.30, atomic weight of Ar = 40.
7.
A 5L vessel contains 1.4g of nitrogen. when heated to 1800 K,30% of molecules are dissociated into atoms. Calculate the pressure of the gas at 1800 K.
8.
A measured temperature on Fahrenheit scale is 200o F. What will this reading be on Celsius scale?
9.
What is meant by reaction quotient?
10.
What is salt bridge?
11.
Write the type of hybridization involved in CH4 C2H4 and C2H2.
12.
Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
13.
What is drikold and for what purpose it is used?
14.
Complete the following reactions.
\({ O }_{ 2 }^{ - }\) + H2 O \(\longrightarrow \)
15.
If 0.561 KOH is dissolved in water to give 200 mL of solution at 298 K calculate the concentrations of potassium, hydrogen and hydroxyl ions. What is its pH?
16.
Does the oxidation number of an element in any molecule or any polyatomic ion represent the actual charge on it?
17.
When 430 J of work was done on a system, it lost 120 J of energy as heat.Calculate the value of internal energy change(\(\Delta U\)) for this process.
18.
Use the information and data given below to answer the question, stronger intermolecular forces result in higher boiling point.
Strength of London forces increases with the number of electrons in the molecules. The boiling point of HF, HCI, HBr, and HI are 293 K, 189 K, 206 K and 238 K respectively.
Why is the boiling point of hydrogen fluoride highest while that of hydrogen chloride lowest?
19.
In Milikan’s experiment, static electric charge on the oil drops has been obtained by shining X-rays. If the static electric charge on the oil drop is –1.282 × 10–18C, calculate the number of electrons present on it.
20.
One mole of any substance contains 6.022\( \times\)1023 atoms / molecules.Number of molecules of H2SO4 present in 100 mL of 0.02 M H2SO4. What will be the solution?
21.
How will you distinguish between Na2CO3 and NaHCO3
22.
A compound made up of two elements A and B has A = 70%, B = 30%. Their relative number of moles in the compound are 1.25 and 1.88. Calculate molecular formula of the compound, if its molecular mass is found to be 160.
23.
Explain the nature of boric acid as a Lewis acid in water?
24.
Lithium is the only alkali metal that forms nitride directly on reaction with air. Explain.
25.
Explain the physical significance of van derWaals' parameters.
1.
They are always univalent because after losing one electron, they aquire nearest inert gas configuration.Li+ forms largest hydrated cations because it has the highest hydration energy.
2.
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chlorine is an oxidant and K2MnO4 is reductant.
3.
The elements of s and p-block are collectively called representative or main group elements. These include elements of group I (alkali metals), group 2 (alkaline earth metals).
4.
44.8 litres of sulphur dioxide at N. T.P.
22.4 litres of sulphur dioxide at N.T.P. = 1 mol
44.8 litres of sulphur dioxide at N.T.P. =\(\frac { 1 \ mol }{ (22.4 \ L) } \) x (44.8L) = 2.0 mol
5.
(i) \({ CH }_{ 2 }={ CH }_{ 2 },CH_{ 3 }CH={ CH }_{ 2 },CH_{ 3 }{ CH }_{ 2 }CH={ CH }_{ 2 },CH_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }CH={ CH }_{ 2 }\)
(ii) \(HCOOH,{ CH }_{ 3 }COOH,{ CH }_{ 3 }{ CH }_{ 2 }COOH,{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }COOH\)
(iii) \({ CH }_{ 3 }CO{ CH }_{ 3 },{ CH }_{ 3 }{ CH }_{ 2 }CO{ CH }_{ 3 },{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }CO{ CH }_{ 3 },{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }{ CH }_{ 2 }CO{ CH }_{ 3 }\)
(iv) \({ CH }_{ 3 }OH,{ CH }_{ 3 }{ CH }_{ 2 }OH,{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }OH,{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }{ CH }_{ 2 }OH\)
(v) \(\\ HC\equiv CH,{ CH }_{ 3 }C\equiv CH,{ CH }_{ 3 }{ CH }_{ 2 }C\equiv CH,{ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }\equiv CH\)
6.
q = 2.303 nRT log \(\frac { { V }_{ 2 } }{ V_{ 2 } } \) = 2.303\(\times \frac{10}{40}\times log\frac{5}{10}\)
=-103.635 cal
For isothermal expansion, \(\Delta\)U = 0 ...........(i)
W = \(\Delta\)U - q = 0 - (-103.635)
= +103.635 cal
Also, when temperature is constant,
p1V1 = p2V2 or pV = constant
\(\Delta\)H = \(\Delta\)E + \(\Delta\)(pV) = 0 + 0 = 0 ..........(ii)
7.
N2 \(\Longleftrightarrow \) 2N
Initial moles
\(\cfrac{1.4}{28}=0.05\)
Final moles
\(0.05-\cfrac{30}{100}\times0.05 \ 2\times0.015\)
Dissociation = 0.05 - 0.015 = 0.035 = 0.030
\(\therefore\) Total number of moles = 0.035 + 0.030 = 0.065
i.e. n = 0.065 mol, V = 5 L, T = 1800 K, p = ?
From pV = nRT, we get
p = \(\cfrac{nRT}{V}\)
= 1.92 atm
8.
There are three common scales to measure temperature oC (degree celsius), oF(degree Fahrenheit) and K (kelvin). The K is the SI unit.
The temperature on two scales are related to each other by the following relationship \(^{ 0 }F=\frac { 9 }{ 5 } t^{ 0 }C+32\)
Putting the values in above equation.
\(200-32=\frac { 9 }{ 5 } t^{ 0 }C\Rightarrow \frac { 9 }{ 5 } t^{ 0 }C=168\)
\(\Rightarrow \ t^{ 0 }C=\frac { 168\times 5 }{ 9 } =93.3^{ 0 }C\)
9.
It is defined as the ratio of product of molar concentration of products to the product of molar concentration of reactants at any stage of reaction.
Qc = \(\frac { \left[ C \right] ^{ c }\left[ D \right] ^{ d } }{ \left[ A \right] ^{ a }\left[ B \right] ^{ b } } \)
for the reaction
aA + bB ⇌ cC + dD
10.
It is a U-shaped tube filled with agar-agar containing inert electrolyte like KCl or KN03 which does not react with solutions
11.
CH4 = sp3
CH = sp2
C2H2 = sp
12.
Benzene is a planar molecule having delocalized electrons above and below the plane of ring. Hence, it is electron-rich. As a result, it is highly attractive to electron deficient species i.e., electrophiles.
Therefore, it undergoes electrophilic substitution reactions very easily.

Nucleophiles are electron-rich. Hence, they are repelled by benzene. Hence, benzene undergoes nucleophilic substitutions with difficulty.
13.
Solid carbon dioxide is known as dry ice.It is soft, white snow like substances and looks like ice.However, it does not wet a piece of cloth or paper because it sublimes without melting.Solid carbon dioxide is used as a refrigerant under the commercial name of drikold.
14.
Superoxides react with water to form H2O2 and O2.
2\({ O }_{ 2 }^{ - }\) + 2 H2 O \(\longrightarrow \) 2 OH- + H2 O2 + O2
15.
\( {[K O H]=\frac{0.561}{56} \times \frac{1000}{200} M=0.050 M} \)
\( \text { As } K O H \rightarrow K^{\oplus}+\stackrel{\ominus}{O} H, \therefore\left[K^{\oplus}\right]=[\stackrel{\ominus}{O H}]=0.05 M \)
\( {\left[H^{\oplus}\right]=K_w /\left[{ }^{\Theta} \mathrm{O} H\right]=10^{-14} / 0.05=10^{-14}} \)
\(\left(5 \times 10^{-2}\right) \)
\(=2.0 \times 10^{-13} M, p H=12.7\)
pH = 12.7
16.
No, the oxidation number of an element in any species is an apparent charge on the atom which it appears to have acquired when all other atoms in the species are removed as ions.
17.
Q = \(\Delta U\) + w
w = 430 on system
Heat lost (Q) = -120
\(\Delta U\) = q - w
= -120 - 430
= +310 J
18.
From the information and data given in the question, we concluded that Hydrogen fluoride has highest dipole moment is due to highest electronegativity of fluorine as well as due to the presence of hydrogen bonding in HF. Therefore, HF has highest boiling point.
19.
Charge on the oil drop = 1.282 ×10–18C
Charge on one electron = 1.6022 × 10–19C
∴ Number of electrons present on the oil drop
\(=\frac{−1.282 × 10^{−18}C}{−1.6022×10^{−19}C}\)=0.800×10=8.0 electrons
20.
One mole of any substance contains 6.022\( \times\)1023 atoms /molecules
Hence, number of millimoles of H2SO4
= molarity \( \times\) volume in mL
= 0.02 \( \times\)100
= 2millimoles
= 2\( \times\) 10-3 mol
Number of molecules = number of moles \( \times\) NA
= 2\( \times\)10-3\( \times\)6.022\( \times\)1023
=12.044 x 1020 molecules
21.
Sodium bicarbonate (NaHCO3) on hetaing composes to produces CO2 gas which whwn pases thrugh lime water, turns milky.
2NaHCO3 \(\xrightarrow[]{\Delta}\)Na2CO3 + CO2 + H2O
Ca(OH)2(aq) + CO2(s)\(\rightarrow \)CaCO3(s) + H2O(l)
But Na2CO3 (Sodium carbonate is stable to heat does not decompose to heat).
22.
Calculation of molecular formula
Empirical formula mass =
\(2\times 56+3\times 16=160\)
\(n=\frac { molecular \ formula }{ empirical \ formula \ mass } =\frac { 160 }{ 160 } =1\)
\(\therefore Molecular\ formula={ A }_{ 2 }{ B }_{ 3 }\)
23.
( )
It is not a protic acid because it does not ionise in H2 O to give a proton. It acts as a Lewis acis by accepting electrons from a hydroxyl ion of water and in turn releases H+ ions.
B(OH)3 + HOH\(\longrightarrow \)[B(OH)4]- + H+
24.
( )
Li+ ion being small in size can easily stablize small nitride ion N3-,however other alkali metal ions because of their larger size cannot stablise smaller nitride ion.Thus,only lithium forms nitride.
25.
( )
a is measure of magnitude of intermolecular forces of attraction while b is a measure of the effective volume of the gas molecules.Value of a and b depends upon the characteristics of a gas.
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