The p-Block Elements

The temperature at which phosphine solidifies is____

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On cooling to -185.5 K, phosphine condenses to a liquid and on cooling to -139.5 K, it solidifies.

Liquid sulphur dioxide is used as a refrigerant because

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Liquid sulphur dioxide is used as a refrigerant because it can be liquefied and re-evaporated easily.

The decreasing order of the covalent character of N, P, As, Sb and Bi is ____ .

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Elements of group 15 form both ionic [BiF3, SbF3] and covalent compounds [NCl3, PCl3 etc] in +3 oxidation state. All the compounds of this group having +5 oxidation states are essentially covalent. Thus, the covalent character decreases on moving down the group forming the order N > P > As > Sb > Bi.

The balanced equation for hydrolysis of XeF4 is ____ .

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On hydrolysis, XeF4 gives 6XeF4 + 12H2O ----------4Xe + 2XeO3 + 24HF + 3O2

Which compound has been identified only by radio tracer technique?

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Compounds of radon [KrF2] have not been isolated but only identified by radio tracer technique.

H2P2O6, on treatment with water, gives ______________ .

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H2P2O6, on treatment with water, gives orthophosphoric acid H3PO4 and orthophosphorus acid H3PO3.

Ozone purifies crowded places because____.

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Since ozone is an endothermic compound, it gets decomposed to oxygen easily. Therefore, it purifies crowded places. 2O3 --------3O2.

The acidic strength of oxoacids of HClO, HClO2, HClO3, HClO4 increases in the order of ____.

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This can be explained based on Lowry Bronsted concept. According to this concept, a strong acid has a weak conjugate base and a weak acid has a strong conjugate base. Thus the order follows: HClO <HClO2 < HClO3 <HClO4.

The allotrope of sulphur which is regarded as super cooled liquid is ____.

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Plastic sulphur is considered as super cooled liquid. It is a liquid which, due to rapid cooling below its freezing point, has no time to settle in a crystalline form.

The oxidation state of oxygen in O2 is____.

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The oxidation state of oxygen in O2 is zero.

Among HCl, HF, H2O and NH3 which forms a linear polymeric structure due to hydrogen bonding?

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In HCl, there is no hydrogen bonding. HF forms zig zag structure. In water, each molecule is linked to four other molecules and so only ammonia forms a linear polymeric structure.

Dioxygen is a____

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Dioxygen is a powerful oxidising agent and supporter of combustion.

The oxidation state of +7 is observed in which of the following oxides?

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In X2O7, halogen shows +7 oxidation state.

Helium is the most commonly used laboratory material due to ____.

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Helium has an unusual property of diffusion. This makes helium the most commonly used laboratory material. It is used in rubber, glass or plastics.

The acid formed when acetic acid is treated with phosphorus trichloride is____

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When acetic acid is treated with phosphorus trichloride, the products formed are acetyl chloride and phosphoric acid. The reaction is as follows: 3 CH3COOH + PCl3 --------3 CH3COCl + H3PO3.

The hybridization of IF7 is ____.

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The outer electronic configuration of iodine atom is 5s2 5p5. To make seven bonds, one s and two p orbitals are promoted to the higher vacant 5d orbitals as shown in fig.

Nitrogen cannot have five half-filled orbitals because ____ .

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Nitrogen is an element of the second period. Therefore, it does not contain d-orbitals. Since the energy gap between 2s and 3s orbitals is large, a 2s electron cannot be promoted to 3s orbital. So nitrogen cannot have five half-filled orbitals.

The super halogen in Group 17 elements is ____ .

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Fluorine is called a super halogen as it is the most reactive halogen.

Among F, Cl, Br and I, the most electronegative element in the periodic table is____

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The electronegativity value decreases down the group from F to I because the atomic size increases and the effective nuclear charge decreases. Thus, Fluorine is the most electronegative element in the periodic table.

Which of the group 15 elements is/ are a source of sulphides?

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Arsenic is got from arsenopyrites; Antimony is got from stibnite; Bismuth is got from bismuth glance. Arsenopyrites, Stibnite and Bismuth glance are sulphides.

____ is a brown gas compound.

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N2O4, N2O and NO – colorless. NO2 - brown gas.

HCl can be dried only by ____ .

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Since HCl gas is acidic in nature, it can be dried only over acidic dehydrating agent like concentrated sulphuric acid.

The products formed when phosphorus is treated with sulphuric acid are

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The product formed when phosphorus is treated with sulphuric acid is phosphoric acid, sulphur dioxide and water. The reaction follows: P4 + 10H2SO4 ---------4H3PO4 + 10SO2 + 4H2O

What is the number of lone pair of electrons on Xe in XeF6, XeF4 and XeF2 respectively?

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No. of lone pairs in XeF2 = 3, in XeF4 = 2 and in XeF6 = 1.

The colour of the precipitate formed when copper sulphate reacts with phosphine is____

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When bubbled through certain metallic salt solutions, phosphides of the metals get precipitated. 3 CuSO4 + 2 PH3 -------------Cu3P2 + 3 H2SO4 black precipitate.

The atomic and ionic radii of the group 16 elements are smaller due to____

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Group 16 elements show increased effective nuclear charge. As a result, there is greater attraction of the electrons by the nucleus and hence radii are less.

The compound which does not react with red phosphorus is

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Red phosphorus does not react with caustic alkalis. This property is made use in separating red phosphorus from white phosphorus.

The impurity present in impure nitric acid is____

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The impure nitric acid is generally yellow in colour due to the presence of nitrogen dioxide as impurity. Nitric acid containing dissolved nitrogen dioxide is known as fuming nitric acid.

The vapour formed when nitrogen tri-iodide ammoniate is either rubbed or struck against a surface is ____.

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When nitrogen tri-iodide ammoniate is either rubbed or struck against a surface, it explodes with noise, liberating vapours of iodine. 8NH3.NI3 -------5N2 + 9I2 + 6NH4I

Among XeO3 and XeOF4, which has the same number of lone pairs on Xe as in XeF4?

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XeOF4 and XeO3 have only one lone pair of electrons whereas in XeF4, there are 2 lone pairs of electrons.

Class 12th Chemistry - 7 The p-Block Elements MCQs
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Class 12th Chemistry - 7 The p-Block Elements MCQs