Write the molecular formula and structural formula of the following substances. (a) Phosphinic acid. (b) Oleum. (c) Perbromic acid.

Hypophosphorous acid is also known as phosphinic acid. Its molecular formula is H 3 PO 2 . Its structure is shown as: Oleum is also known as disulphuric acid or pyrosulphuric acid. Its molecular formula is H 2 S 2 O 7 . Its structure is shown as: Perbromic acid is the most unstable of the halogen(VII) oxoacids. Its molecular formula is HBrO 4 . Its structure is shown as:

Give reason: Fluorine has only - 1 oxidation state, but other halogens have oxidation states as + 1 , + 3 , + 5 and + 7 also.

All halogens exhibit - 1 oxidation state, because they gain an electron to complete their octet structure. Chlorine, bromine and iodine show + 1 , + 3 , + 5 and + 7 oxidation states in different excited states, but fluorine cannot exhibit the higher oxidation states due to the absence of d -subshell, and inability to expand octet structure. Fluorine cannot show + 1 oxidation state also due to high electronegativity.

Give reason: H 2 O is a liquid and H 2 S is a gas.

Water ( H 2 O ) has oxygen as the central atom. Oxygen has smaller size and higher electronegativity as compared to sulphur. Therefore, there is extensive hydrogen bonding in water molecules, which is absent in hydrogen sulphide ( H 2 S ). Molecules of hydrogen sulphide are held together only by weak van der Waal's forces of attraction. Hence, water exists as a liquid while hydrogen sulphide as a gas.

Give reason: BiH 3 is the strongest reducing agent among all the hydrides of Group- 15 elements.

The reducing property increases from NH 3 to BiH 3 . As we move down the group, the size of the element increases and, therefore, the bond length of the M - H bond increases and consequently its dissociation enthalpy decreases, that enables to provide hydrogen more easily. Hence, BiH 3 is the strongest reducing agent among all hydrides of Group- 15 elements.

Write the complete balanced equation for the following: Cl 2 + NaOH hot and con . →

Chlorine reacts with hot and concentrated sodium hydroxide to give sodium chloride, sodium chlorate and water. The reaction is as given below: 3 Cl 2 + 6 NaOH hot and con . → 5 NaCl + NaClO 3 + 3 H 2 O

Write the complete balanced equation for the following: C + H 2 SO 4 con . →

Carbon, when heated with concentrated sulphuric acid, oxidised to carbon dioxide. Sulphur dioxide and water are the other products of the reaction. The equation is written below: C + 2 H 2 SO 4 con . → 2 H 2 O + CO 2 + 2 SO 2

Write the complete balanced equation for the following: Cu + HNO 3 ( con . ) →

Copper, when reacts with concentrated nitric acid forms cupric nitrate. Reddish brown fumes of nitrogen dioxide is formed. The reaction is as shown below: Cu + 4 HNO 3 ( con . ) → Cu NO 3 2 + 2 H 2 O + 2 NO 2

Give the reaction of dichlorine gas with cold & dilute and hot and concentrated NaOH ( aq ) .

Dichlorine gas reacts with cold and diluted NaOH ( aq ) as follows: Cl 2 + 2 NaOH ( cold and dil . ) → NaCl + NaClO + H 2 O NaCl is called sodium chloride and NaClO is called sodium hypochlorite. In this reaction, the oxidation state of Cl in chlorine gas ( 0 ) is changing to - 1 in NaCl and + 1 in NaClO . Thus, it is a disproportionation reaction. Dichlorine gas reacts with hot and concentrated NaOH and the reaction is as follows: 6 NaOH + 3 Cl 2 → 5 NaCl + NaClO 3 + 3 H 2 O It is also a disproportionation reaction. The oxidation state of chlorine is changing from 0 to − 1 and + 5 .

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 7 - The p-Block Elements>Gujarat Board-2019>Q 12

MEDIUM

12th Gujarat Board

IMPORTANT

Earn 100

Draw structural formula of pyrophosphoric acid and peroxodisulphuric acid.

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