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151.

Assertion (A) The O-O bond length in `H_(2)O_(2)` is shorter than that in `O_(2)`. Reason (R ) `H_(2)O_(2)` is ionic compound.A. Both A and R true and R is the correct explanation of AB. Both A and R true and R is not a correct explanation of AC. A is true but R is falseD. A is false but R is true

Answer» Correct Answer - D
Discussion
152.

Which of the following does not react with `AgCl`?A. `Na_2S_2O_3`B. `NH_4OH`C. `NaNO_3`D. `Na_2CO_3`

Answer» Correct Answer - C
`NaNO_3` does not react with AgCl
`2Na_2S_2O_3+AgCl to underset("Soluble complex")(Na_3[Ag(S_2O_3)_2])+NaCl`
`2NH_4OH + AgCl to underset("Soluble complex")([Ag(NH_3)_2]Cl) + H_2O`
`Na_2CO_3 + 2AgCl to Ag_2CO_3 +2NaCl `
Discussion
153.

A and B are two salts. A reacts both with dil `H_2SO_4` and conc. `H_2SO_4` to give reddish brown vapours. However, B reacts only with conc. `H_2SO_4` to give similar vapours. Hence A and B are respectivelyA. NaBr, `NaNO_3`B. `NaNO_3`, NaBrC. `NaNO_2`, NaBrD. NaBr, `NaNO_2`

Answer» Correct Answer - C
`NaNO_2` gives `NO_2` (brown vapours) both with dil. as well as conc. `H_2SO_4`. However NaBr gives `Br_2` (brown vapours) only with conc. `H_2SO_4`. This is because halides can be decomposed only by conc `H_2SO_4` and not by dil. `H_2SO_4`
Discussion
154.

Which one of the following reacts with conc. `H_2SO_4`?A. AuB. AgC. PtD. Pb.

Answer» Correct Answer - B
Ag reacts with conc. `H_2SO_4`
`({:(H_2SO_4to,H_2O+SO_2+O),(2Ag+H_2SO_4+Oto,Ag_2SO_4+H_2O):})/ul(2Ag+2H_2SO_4to 2H_2O + SO_2 + Ag_2SO_4)`
Pb does not react with conc. `H_2SO_4` . It is due to the formation of insoluble layer of `PbSO_4`
Au and Pt do not react with conc. `H_2SO_4`.
Discussion
155.

Bromine water reacts with `SO_(2)` to formA. `H_2O` and HBrB. `H_2SO_4` + HBrC. HBr and SD. S and `H_2O`

Answer» Correct Answer - B
`({:(Br_2+H_2O" " to,2HBr+O),(SO_2+O+H_2Oto,H_2SO_4):})/ul(Br_2+SO_2+2H_2O to 2HBr+H_2Br_4)`
Discussion
156.

The elements oxygen and sulphur are called chalcogens becauseA. their properties resemble with charcoalB. their properties resemble not only with charcoal but also with halogensC. these are ore forming elementsD. these combine with halogens.

Answer» Correct Answer - C
Chalcogens mean ore forming elements because most of the ores are either oxides or sulphides.
Discussion
157.

By passing `H_(2)S` in acidified `KMnO_(4)` solution we getA. `K_2S`B. SC. `K_2SO_3`D. `MnO_2`

Answer» Correct Answer - B
`KMnO_4//H^(+)` oxidises `H_2S` to S
`({:(2KMnO_4+3H_2SO_4to,K_2SO_4+2MnSO_4+3H_2O+50),(H_2S+O to, H_2O +S"]"xx5):})/ul(5H_2S + 2KMnO_4+3H_2SO_4 to 8H_2O + K_2SO_4 +2MnSO_4+5S)`
Discussion
158.

Oxygen molecule isA. diamagnetic with no-unpaired electron.B. diamagnetic with two unpaired electronsC. paramagnetic with two unpaired electronsD. paramagnetic with no unpaired electron.

Answer» Correct Answer - C
`O_2` is paramagnetic with two unpaired electrons in `pi_(2p_x)^** and pi_(2p_y)^**` antibonding orbitals.
Discussion
159.

Which of the following oxoacids contains more than one S-S bonds ?A. Dithionic acidB. Thiosulfurous acidC. Polythionic acidD. Peroxydisulfuric acid

Answer» Correct Answer - C
Polythionic acid. `HO-undersetunderset(O)(||)oversetoverset(O)(||)S-(S)_n-undersetunderset(O)(||)oversetoverset(O)(||)S-OH`
Discussion
160.

Assertion: `SiF_(6)^(2-)` is known but `SiCl_(6)^(2-)` is not. Reason: Size of fluorine is small and its lone pair of electrons intersects with d-orbitals of `Si` strongly.A. Both A and R true and R is the correct explanation of AB. Both A and R true and R is not a correct explanation of AC. A is true but R is falseD. A is false but R is true

Answer» Correct Answer - A
Discussion
161.

Sodium nitrate decomposes above `800^(@)C` to give :A. `N_2`B. `O_2`C. `NO_2`D. `Na_2O`

Answer» Correct Answer - B
`2NaNO_3 overset(Delta)to 2NaNO_2+O_2`
Discussion
162.

Which of the following is a liquid ?A. `SCl_4`B. `SeCl_4`C. `TeCl_4`D. `PoCl_4`

Answer» Correct Answer - A
Only `SCl_4` is a unstable liquid, all others are stable solids.
Discussion
163.

What is false about oxygen and sulphur ?A. Both can form covalent bond with metalsB. Both exist in diatomic stateC. Both can exhibit O.N. of -2 as well as +2D. Both can form covalent hydrides.

Answer» Correct Answer - B
Actually oxygen is diatomic `(O_2)` while sulphur exists as octa-atomic `(S_8)` bonding.
Discussion
164.

`H_2S` is more acidic than `H_2O`. The reason isA. oxygen is more electronegative than sulphurB. atomic number of sulphur is higher than oxygenC. H-S bond is weaker as compared to H-O bondD. H-O bond is weaker as compared to H-S bond

Answer» Correct Answer - C
Due to larger size of sulphur H-S bond is weaker and breaks easily as compared to H-O bond.
Discussion
165.

Oxygen can be obtained from bleaching powder byA. action of dilute acidsB. heating it with limeC. heating it with a cobalt saltD. action of alkalis.

Answer» Correct Answer - C
`2CaOCl_2 " " .^(CoCl_2)" " 2CaCl_2 + O_2`
Discussion
166.

`[X]+H_(2)SO_(4) rarr [Y]` a colourless gas with irritating smell `[Y] + K_(2)Cr_(2)O_(7) + H_(2)SO_(4) rarr` green solution `[X]` and `[Y]` areA. `SO_3^(2-), SO_2`B. `Cl^(-) , HCl`C. `S^(2-) , H_2S`D. `CO_3^2, CO_2`

Answer» Correct Answer - A
`SO_3^(2)+underset(("from" H_2SO_4))(2H^(+))toSO_2+H_2O`
`3SO_2+Cr_2O_7^(2)+2H^(+)to3SO_4^(2)+underset(("green"))(2Cr^(3+))+H_2O`
Discussion
167.

Which is an oxidising substance amongst the following ?A. `CO_2`B. `NO_2`C. `SO_2`D. `SO_3`

Answer» Correct Answer - D
`SO_3` can act as a strong oxidising agent.
Discussion
168.

Crystalline form of sulphur stable at room temperature isA. Rhombic sulphurB. Monoclinic sulphurC. Plastic sulphurD. Prismatic sulphur

Answer» Correct Answer - A
Crystalline form of sulphur stable at room temperature is rhombic sulphur.
Discussion
169.

Which is most acidic in nature ?A. `Na_2O`B. MgOC. `Al_2O_3`D. CaO

Answer» Correct Answer - C
`Na_2O, MgO and CaO` are distinctly basic. `Al_2O_3` is atphoteric . Thus, out of the given four oxides `Al_2O_3` is most acidic
Discussion