CBSE Class 12 Chemistry The p Block Elements Worksheet Set A

Question. Which of the following will show highest solubility in water?
(a) NH₃
(b) PH₃
(c) AsH₃
(d) SbH₃
Answer. A

Question. Pure nitrogen is obtained from
(a) NH₃ + NaNO₃ 
(b) N₂O + Cu
(c) NH₄ Cl +NaNO₂ 
(d) (NH₄)₂ Cr₂O₇
Answer. D

Question. Which of the following products will be obtained on heating ammonium dichromate?
(a) Chromium oxide and ammonia
(b) Chromic acid and ammonia
(c) Chromic acid and nitrogen
(d) Chromium oxide and nitrogen
Answer. D

Question. Large scale manufacture of nitric acid by Ostwald process takes place using the reaction
(a) 2NaNO₃ H₂SO₄ →Na₂SO₄  + 2HNO₂
(b) 4NH₃ 5O₂→ 4NO +6H₂O 
(c) NO⁺₂ + NO^-₃ +H₂O→2HNO₃
(d) 2NO +O₂+ H₂O →HNO₃+ HNO₂ 
Answer. B

Question. Which among the following metals when treated with dil. HNO₃ , will produce nitrous oxide?
(a) Fe
(b) Zn
(c) Cu
(d) Ag
Answer. B

Question. Production of nitrogen (I) oxide takes place by
(a) thermal decomposition of ammonium nitrate
(b) interaction of hydroxyl amine and nitric acid
(c) disproportionation of N₂O₄
(d) substitution of ammonium sulphate
Answer. A

Question. Nitric oxide can be synthesised in the laboratory by
(a) treating Zn with cold and dilute HNO₃
(b) treating Zn with concentrated HNO₃
(c) treating copper with cold and dilute HNO₃
(d) heating NH₄NO₃
Answer. C

Question. Which among the following products is obtained when oxygen is passed through a solution of Na₂ SO₃?
(a) Na₂ SO₄
(b)Na₂ S 
(c) NaHSO₄
(d) NaH
Answer. A

Question. Which of the following will not yield oxygen on reaction with ozone?
(a) H₂O₂
(b) SO₂
(c) KI
(d) Hg
Answer. B

Question. Ozone (O ) 3 reacts with potassium iodide in a neutral medium. What will be the product obtained?
(a) KCl
(b) KOH
(c) KIO₃
(d) KO₂
Answer. B

Question. What change is observed if SO₂ is passed through acidified K₂Cr₂ O₇ solution?
(a) The solution turns blue
(b) The solution gets decolourised
(c) SO₂ is reduced
(d) Green Cr₂(SO)₃ is formed
Answer. D

Question. Complete the following analogy.
Powerful oxidising agent : A : : Least active halogen : B
(a) A : Fluorine, B : Iodine
(b) A : Chlorine, B : Fluorine
(c) A : Iodine, B : Bromine
(d) A : Bromine, B: Chlorine
Answer. A

Question. On hydrolysis of ClF, it forms
(a) HCl + HOF
(b) Cl₂O+ HF
(c) HOCl + HF
(d) None of these
Answer. C

Question. Which of the following is correct order of bond angles?
(a) H₂ O>OF₂ >Cl₂ O>ClO₂
(b) OF₂ >OCl₂ >H₂O>ClO₂
(c) ClO₂ > Cl₂O>H₂O>OF₂
(d) OF₂ >H₂O >Cl₂O>ClO₂
Answer. C

Question. The oxidation number of xenon is .......
(a) zero
(b) 2
(c) 4
(d) 1
Answer. C

Very Short Answer

Question. Which element is synthetic radioactive element?
Answer. Moscovium is a synthetic radioactive element.

Question. Which groups is p- blocks elements?
Answer. The p-block contains groups 13, 14, 15, 16, 17, and 18, with the exception of Helium.

Question. Which essential constituent of animal and plant matter?
Answer. Phosphorus is an essential constituent of animal and plant matter.

Question. What kinds of proteins are present in the milk and eggs?
Answer. Phosphoproteins are present in the milk and eggs.

Question. What is the use of liquid dinitrogen?
Answer. Liquid detergents are used as refrigerant to preserve biological materials, food items and in cryosurgery.

Short Answer

Question. What are the properties of the dinitrogen?
Answer. Properties of dinitrogen are:
1. Dinitrogen is colourless, tasteless and odourless.
2. Dinitrogen is non- toxic gas.
3. Dinitrogen has a very low solubility.
4. Dinitrogen has low freezing and boiling points.

Question. Why does NH₃ act as a Lewis base
Answer. The nitrogen atom in ammonia has a lone pair of electrons which can be easily donated to suitable Lewis acid. So, ammonia can act as a Lewis base. A Lewis base may be defined as a compound which donates a pair of electron to other chemical species. in NH3 molecule the central atom nitrogen has 5 electron in its outermost orbit (2s2,2p3).

Question. What are the occurrence of group 15 elements
Answer. Group 15 elements include nitrogen, phosphorus, arsenic, antimony and bismuth.Nitrogen is the real constituent of the air and records for 78% of it by volume. It is the primary member of this group and happens in a free state as a diatomic gas, N2.

Question. What do you understand by dinitrogen?
Answer. Dinitrogen constitutes almost 78% of the earth’s atmosphere. It is the most available element present in the air. It is the seventh most abundant uncombined element found in the universe. It is mainly used in the industrial manufacturing of compounds such as ammonia, calcium cynamide etc. It is used in the manufacturing industries such as iron and steel to obtain an inert atmosphere.

Question. What are the uses of ammonia?
Answer. Ammonia is used as a refrigerant gas, for purification of water supplies, and in the manufacture of plastics, explosives, textiles, pesticides, dyes and other chemicals. It is found in many household and industrial-strength cleaning solutions.

Long Answer

Question. Explain the Brown Ring test which is used in nitric acid?
Answer. The brown ring test is performed for the qualitative detection of nitrates. The brown ring test is performed by putting iron (II) sulphate to a solution that contains nitrate ions. After that, slowly and carefully add concentrated sulphuric acid without disturbing the solution so that a sulphuric acid layer is formed under the aqueous solution. If nitrate is present, a brown ring consisting of [Fe (H₂O) ₅NO] SO₄ will form at the junction of the two layers. Brown ring test is used for the detection of nitrate ions in a solution. It detects the presence of the nitrate ions by the formation of brown ring at the junction of two layers of the solution. This brown coloured ring is formed because of the formation of the brown coloured iron complex is called brown ring complex. Brown ring test is useful or sensitive up to 2.5 micrograms and a concentration of 1 in 25,000 parts. Brown ring test is used for the detection of the nitrate. It is used to detect the presence of the nitrate in many food samples. A common nitrate test, known as the brown ring test can be performed by adding iron (II) sulphate to a solution of a nitrate, then slowly adding concentrated sulphuric acid such that the acid forms a layer below the aqueous solution.

Question. Difference between atomic radius and ionic radius
Answer.
1. Atomic radius is the radius of a neutral atom whereas ionic radius is the radius of an atom’s ion.
2. Atomic radius can be calculated as the distance from the nucleus of an atom to its boundary of the electron cloud whereas ionic radius can be calculated by dividing the distance between two nuclei of two ions according to their sizes.
3. In atomic radius the neutral atoms of the same element have the same size, so the atomic radius is equal to each other whereas in ionic radius the cations have a smaller atomic radius than that of anions.
4. Atomic radius is determined considering neutral gaseous atoms of chemical elements whereas ionic radius is determined considering cations and anions that are in an ionic bond (in ionic compounds).

Question. Explain the anomalous properties of nitrogen?
Answer. Nitrogen differs from of the members of this group due to its small size, high electronegativity, high ionisation enthalpy and non-availability of d orbitals, pπ -pπ multiple bonds with itself and with other elements having small size and high electronegativity. Anomalous properties of the nitrogen are:
1. Reactivity towards hydrogen: all the elements of the group 15 from hydrides of the type EH₃. When two molecules of nitrogen react with three molecules of the hydrogen in the presence of catalyst they form two molecules of ammonia.Ammonia is only a mild reducing agent, BiH₃ id the strongest reducing agent amongst all the hydrides.
2. Reactivity towards oxygen: Oxygen is very reactive with Alkali metals. Alkali metals are given the name alkali because the oxides of these metals react with water to form a metal hydroxide that is basic or alkaline. Lithium produces an oxide, sodium produces peroxide, and potassium, cesium, and rubidium produce super oxides.
3. Reactivity towards halogens: Halogens are highly reactive, and they can be harmful or lethal to biological organisms in sufficient quantities. This reactivity is due to high electronegativity and high effective nuclear charge. Halogens can gain an electron by reacting with atoms of other elements. Fluorine is one of the most reactive elements.
4. Reactivity towards metals: The molecular compounds of nitrogen are formed by the direct reaction of the elements. At elevated temperatures, nitrogen reacts with highly electropositive metals to form ionic nitrides, such as Li3N and Ca₃N₂.
These compounds consist of ionic lattices formed by Mⁿ⁺ and N³⁻ ions

Question. What are the atomic, chemical and physical properties of the group 15 elements?
Answer.
The atomic, chemical and physical properties of the group 15 elements are:
1. Electronic configuration: The group 15 elements consist of five valence electrons. Due to this the elements can either lose five electrons or gain three electrons in order to attain the stable configuration. The general electronic configuration of nitrogen family is ns²np³.
2. Atomic and ionic radii: covalent and ionic radii increase in the size down the group. There is a considerable increase in covalent radius from N to P. New orbitals increase both the Atomic and the Ionic radii of group 15 elements.
3. Ionisation enthalpy: Ionization Energy is the amount of energy required to remove an electron from the outermost orbit of the atom. Ionisation enthalpy decreases down the group due to the gradual increase in atomic size, because of the extra stable half-filled p orbitals electronic configuration and smaller size, the ionisation enthalpy of group 15 elements is much greater than that of the group 14 elements in the corresponding periods.
4. Electronegativity: The electronegativity value decreases down the group with increasing atomic size. This again is due to the increasing distance between the nucleus and the valence shell as we move down the group.
5. Physical properties: Physical properties incorporate physical state, boiling and melting points, metallic character, allotropy, and density. Nitrogen is a diatomic gas, while the rest of the elements are solids in nature.
6. Trends in melting and boiling points: The melting point increments from nitrogen to arsenic because of the continuous increment in nuclear size. The low melting point of nitrogen is because of its discrete diatomic particles.

Question. State the difference between white phosphorus and red phosphorus?
Answer.
1. Red phosphorous is an allotrope of phosphorous that has a dark red colour whereas white phosphorous is an allotrope of phosphorous that exists as translucent waxy solids.
2. Red phosphorous is not phosphorescent whereas white phosphorous is phosphorescent.
3. Red phosphorous exists as a polymeric network whereas white phosphorous exists as P4 molecules.
4. Red phosphorous is non-toxic and less reactive whereas white phosphorous is toxic and highly reactive.
5. Red phosphorus appears as dark red coloured crystals whereas white phosphorus becomes yellow when exposed in light.

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