CBSE 12th Standard Chemistry Subject The p-Block Elements Chapter Case Study Questions 2021
QB365 Provides the updated CASE Study Questions for Class 12 , and also provide the detail solution for each and every case study questions . Case study questions are latest updated question pattern from NCERT, QB365 will helps to get more marks in Exams
QB365 - Question Bank Software
CBSE 12th Standard Chemistry Subject The p-Block Elements Case Study Questions 2021
12th Standard CBSE
-
Reg.No. :
Chemistry
-
Read the passage given below and'answer the following questions :
Ozone is an unstable, dark blue diamagnetic gas. It absorbs the UV radiation strongly, thus protecting the people on earth from the harmful UV-radiation from the sun. The use of chlorofluorocarbon (CFC) in aerosol and refrigerators and their subsequent escape into the atmosphere, is blamed for making holes in the ozone layer over the Antarctica. Ozone acts as a strong oxidising agent in acidic and alkaline medium. For this property, ozone is used as a germicide and disinfectant for sterilizing water. It is also used in laboratory for the ozonolysis of organic compounds and in industry for the manufacture of potassium permanganate, artificial silk, etc
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following statements is not correct for ozone?(a) It oxidises lead sulphide (b) It oxidises potassium iodide (c) It oxidises mercury. (d) It cannot act as bleaching agent in dry state. (ii) Ozone reacts with moist iodine gives
(a) HI (b) HIO3 (c) I2O5 (d) I2O4 (iii) Ozone acts as an oxidising agent due to
(a) liberation of nascent oxygen (b) liberation of oxygen gas (c) both (a) and (b) (d) none of these (iv) The colour of ozone molecule is
(a) white (b) blue (c) pale green (d) pale yellow. -
Read the passage given below and answer the following questions :
Chlorine is a greenish yellow gas with pungent and suffocating odour. With dry slaked lime, it gives bleaching powder. Bleaching powder is a mixture of calcium hypochlorite and basic calcium chloride :
[Ca(OCI)2. CaCl2 ·Ca(OH)2· 2 H2O].
The amount of chlorine obtained from a sample of bleaching powder by the treatment with excess of dilute
acids or CO2 is called available chlorine. Chlorine is a powerful bleaching agent. Bleaching effect of chlorine is permanent.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Chlorine gas reacts with_____to form bleaching powder(a) Ca(OH)2 (b) CaCl2 (c) CaSO4 (d) dry CaO (ii) Chlorine reacts with cold and dilute alkali to form
(a) chloride (b) hypochlorite (c) chlorate (d) both (a) and (b) (iii) Chlorine is used as a bleaching agent. The bleaching action is due to
(a) oxidation (b) chlorination (c) hydrogenation (d) reduction (iv) Bleaching powder contains a salt of an oxoacid as one of its components. The anhydride of that oxoacid is
(a) Cl20 (b) Cl2O7 (c) CIO2 (d) Cl2O6 -
Read the passage given below and answer the following questions :
The halogen elements show great resemblances to one another in their chemical behaviour and properties of their compounds with other elements. There is, however, a progressive change in properties from F through Cl, Br, and I to At. F is most reactive among the halogens and infact, from all other elements and it has certain other properties that set it apart from the other halogens.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.(a) Assertion and reason both are correct statements and reason is correct explanation for assertion. (b) Assertiqn and reason both are correct statements but reason is not correct explanation for assertion. (c) Assertion is correct statement but reason is wrong statement (d) Assertion is wrong statement but reason is correct statement. (i) Assertion: F2 has high reactivity.
Reason: F2 has low bond dissociation enthalpy
(ii) Assertion: The bond between F - F is weaker than between Cl - Cl.
Reason : Atomic size of F is smaller than that of Cl.
(iii) Assertion: F atom has less negative electron affinity than Cl atom.
Reason: Additional electrons are repelled more effectively by 3p- electrons in Cl than by 2p- electrons in F atom.
(iv) Assertion : Fluorine is strongest oxidising agent in halogens.
Reason : It displaces other halogens from its aqueous solution. -
Read the passage given below and answer the following questions :
All the elements of group 16 form hydrides : H2O, H2S, H2Se, H2Te and H2Po. All these hydrides have angular structure which involves sp3 hybridisation of the central atom. All hydrides are volatile. The volatility increases from H2O to H2S and then decreases. All hydrides are weakly acidic in character. The increase in acidic characterfrom H2O to H2 Te is a result of the decrease in the 1 H- E (where E = 0, S, Se, Te, Po) bond dissociation enthalpy from H2O to H2Te. All the hydrides except water are reducing agents. The reducing property of these hydrides increases from H2S to H2Te.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement
(i) Assertion: Water has high boiling -point.
Reason: Water molecules are associated with hydrogen bonding.
(ii) Assertion: H2Te has less acidic character than H2S.
Reason: Bond dissociation enthalpy of H - Te is less than H - S.
(iii) Assertion: Reducing nature of hydrides of group-16 elements increases as the atomic number of central
atom increases.
Reason : Due to strong force of attraction of H - E bond.
(iv) Assertion: H2O is the only hydrides of the chalcogens which is liquid.
Reason : In ice each a-atom is surrounded by 4H -atoms.
*****************************************
CBSE 12th Standard Chemistry Subject The p-Block Elements Case Study Questions 2021 Answer Keys
-
(i) (d)
(c) : Ozone reacts with alkenes to form ozonides which on hydrolysis or reduction gives carbonyl compounds.
(ii) (b) : \(\mathrm{I}_{2}+5 \mathrm{O}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{HIO}_{3}+5 \mathrm{O}_{2}\)
(iii) (a)
(iv) (b) -
(i) (a)
(ii) (d) : In cold, chlorine reacts with dilute alkalies to form chlorides and hypochlorites.
(iii) (a) : \(\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow 2 \mathrm{HCl}+[\mathrm{O}]\)
(iv) (a) : Bleaching powder contains OCl- ion, hence the oxoacid is HOCI. Anhydride of HOCI is Cl2O.
-
(i) (a) : Fluorine is most electronegative element and has low bond dissociation enthalpy.
(ii) (a) : In F - F bond, due to smaller size of fluorine, e--e- repulsion occur, so its bond strength is less.
(iii) (c) : Additional electrons are repelled more effectively by 2p-electrons in F than by 3p- electrons in CI atom.
(iv) (b) : The electrode potential of F2 is maximum while that of I2is minimum. -
(i) (a) :The high boiling point of water is due to the association of H2O molecules through hydrogen bonding.
(ii) (d) : H2Te is more acidic than H2S.
(iii) (c) : Due to weakening of H-E bond as the bond length increases with increase of size of E-atom.
(iv) (b)
