Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

P Block Elements question

2010 · Shift 2 · Q8
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Advanced
  3. /Chemistry
  4. /P Block Elements
  5. /2010 · Shift 2 · Q8

P Block Elements question

2010 · Shift 2 · Q8

JEE AdvancedChemistryP Block ElementsNumerical+2 / −1
The total number of diprotic acids among the following is: H3PO4H_3PO_4H3​PO4​, H2SO4H_2SO_4H2​SO4​, H3PO3H_3PO_3H3​PO3​, H2CO3H_2CO_3H2​CO3​, H2S2O7H_2S_2O_7H2​S2​O7​, H3BO3H_3BO_3H3​BO3​, H3PO2H_3PO_2H3​PO2​, H2CrO4H_2CrO_4H2​CrO4​ and H2SO3H_2SO_3H2​SO3​
Numerical answer
View written solutionFree

Correct answer: 6

A diprotic acid is an acid that can donate two protons (H+H^+H+ ions) per molecule upon dissociation in water. The number of donatable protons is also known as the basicity of the acid. For oxyacids, the basicity is generally determined by the number of hydroxyl (-OH) groups directly bonded to the central non-metal atom, as the hydrogen atom in the -OH bond is ionizable.

Let's analyze each acid provided in the list to determine its basicity.

  1. H3PO4H_3PO_4H3​PO4​ (Phosphoric acid): The structure of phosphoric acid has a central phosphorus atom bonded to one oxygen atom via a double bond and to three hydroxyl (-OH) groups. Structure: O∥∥HO−P−OH∣OH\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -P- & OH \\ & | & \\ & OH & \end{matrix}Structure: HO​O∥∥−P−∣OH​OH​ Since there are three -OH groups, it can donate three protons. Thus, it is a triprotic acid.

  2. H2SO4H_2SO_4H2​SO4​ (Sulfuric acid): The structure of sulfuric acid has a central sulfur atom bonded to two oxygen atoms via double bonds and to two hydroxyl (-OH) groups. Structure: O∥∥HO−S−OH∥∥O\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -S- & OH \\ & \|\| & \\ & O & \end{matrix}Structure: HO​O∥∥−S−∥∥O​OH​ It has two -OH groups, so it can donate two protons. Thus, it is a diprotic acid.

  3. H3PO3H_3PO_3H3​PO3​ (Phosphorous acid): The structure of phosphorous acid has a central phosphorus atom bonded to one oxygen atom via a double bond, two hydroxyl (-OH) groups, and one hydrogen atom directly. The H atom directly bonded to the P atom is not ionizable. Structure: O∥∥HO−P−OH∣H\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -P- & OH \\ & | & \\ & H & \end{matrix}Structure: HO​O∥∥−P−∣H​OH​ It has two -OH groups, so it can donate two protons. Thus, it is a diprotic acid.

  4. H2CO3H_2CO_3H2​CO3​ (Carbonic acid): The structure of carbonic acid has a central carbon atom bonded to one oxygen atom via a double bond and to two hydroxyl (-OH) groups. Structure: O∥∥HO−C−OH\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -C- & OH \end{matrix}Structure: HO​O∥∥−C−​OH​ It has two -OH groups, so it can donate two protons. Thus, it is a diprotic acid.

  5. H2S2O7H_2S_2O_7H2​S2​O7​ (Pyrosulfuric acid or Oleum): This acid has two sulfur atoms linked by an oxygen bridge. Each sulfur atom is bonded to two other oxygen atoms (double bond) and one hydroxyl (-OH) group. Structure: OO∥∥∥∥HO−S−O−S−OH∥∥∥∥OO\text{Structure: } \quad \begin{matrix} & O & & O & \\ & \|\| & & \|\| & \\ HO & -S- & O & -S- & OH \\ & \|\| & & \|\| & \\ & O & & O & \end{matrix}Structure: HO​O∥∥−S−∥∥O​O​O∥∥−S−∥∥O​OH​ It has two -OH groups in total, so it can donate two protons. Thus, it is a diprotic acid.

  6. H3BO3H_3BO_3H3​BO3​ (Boric acid): Boric acid has a central boron atom bonded to three hydroxyl (-OH) groups. However, it does not donate protons from its -OH groups. Instead, it acts as a weak Lewis acid by accepting a hydroxide ion (OH−OH^−OH−) from water, which releases a proton. B(OH)3+H2O⇌[B(OH)4]−+H+B(OH)_3 + H_2O \rightleftharpoons [B(OH)_4]^- + H^+B(OH)3​+H2​O⇌[B(OH)4​]−+H+ Since it releases only one proton per molecule, it is a monoprotic acid.

  7. H3PO2H_3PO_2H3​PO2​ (Hypophosphorous acid): The structure has a central phosphorus atom bonded to one oxygen atom via a double bond, one hydroxyl (-OH) group, and two hydrogen atoms directly. The H atoms directly bonded to the P atom are not ionizable. Structure: O∥∥H−P−OH∣H\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ H & -P- & OH \\ & | & \\ & H & \end{matrix}Structure: H​O∥∥−P−∣H​OH​ It has only one -OH group, so it can donate only one proton. Thus, it is a monoprotic acid.

  8. H2CrO4H_2CrO_4H2​CrO4​ (Chromic acid): The structure is analogous to sulfuric acid, with a central chromium atom bonded to two oxygen atoms via double bonds and to two hydroxyl (-OH) groups. Structure: O∥∥HO−Cr−OH∥∥O\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -Cr- & OH \\ & \|\| & \\ & O & \end{matrix}Structure: HO​O∥∥−Cr−∥∥O​OH​ It has two -OH groups, so it can donate two protons. Thus, it is a diprotic acid.

  9. H2SO3H_2SO_3H2​SO3​ (Sulfurous acid): The structure has a central sulfur atom bonded to one oxygen atom via a double bond and to two hydroxyl (-OH) groups (and a lone pair of electrons). Structure: O∥∥HO−S−OH\text{Structure: } \quad \begin{matrix} & O & \\ & \|\| & \\ HO & -S- & OH \end{matrix}Structure: HO​O∥∥−S−​OH​ It has two -OH groups, so it can donate two protons. Thus, it is a diprotic acid.

Conclusion: From the analysis, the diprotic acids in the given list are:

  1. H2SO4H_2SO_4H2​SO4​
  2. H3PO3H_3PO_3H3​PO3​
  3. H2CO3H_2CO_3H2​CO3​
  4. H2S2O7H_2S_2O_7H2​S2​O7​
  5. H2CrO4H_2CrO_4H2​CrO4​
  6. H2SO3H_2SO_3H2​SO3​

The total number of diprotic acids is 6.

PreviousNext

More from P Block Elements

  • The reaction of P 4​ with X leads selectively to P 4​ O 6​. The X is2009 · MCQ
  • Match each of the reactions given in Column I with the corresponding product(s) given in Column II: Includes table2009 · MCQ
  • In the reaction 2X+B2​H6​→[BH2​(X)2​]+[BH4​]− the amine(s) X is(are) :2009 · Multiple correct
  • The nitrogen oxide(s) that contain(s) N-N bond(s) is(are)2009 · Multiple correct
  • A solution of colourless salt H on boiling with excess NaOH produces a non-flammable gas. The gas evolution ceases after sometime. Upon addition of Zn dust to the same solution, the gas evolution restarts. The colourless salt(s) H is(are):2008 · Multiple correct
  • Statement 1 : Pb 4+ compounds are stronger oxidising agents than Sn 4+ compounds. and Statement 2 : The higher oxidation states for the group 14 elements are more stable for the heavier members of the group due to 'inert pair…2008 · MCQ
  • There are some deposits of nitrates and phosphates in earth's crust. Nitrates are more soluble in water. Nitrates are difficult to reduce under the laboratory conditions but microbes do it easily. Ammonia forms large number of complexes…2008 · MCQ
  • There are some deposits of nitrates and phosphates in earth's crust. Nitrates are more soluble in water. Nitrates are difficult to reduce under the laboratory conditions but microbes do it easily. Ammonia forms large number of complexes…2008 · MCQ