Chapter 4, Problem 2STP

Interpretation Introduction

Interpretation:

The compound whose formula is not correct is to be chosen.

Concept introduction:

To name a compound, certain rules are followed. The given compounds are binary compounds.

Binary compounds are of three types:

• Type-I: Compound in which a metal forms ionic bond with a non-metal and the metal can form only one type of ions.
• Type-II: Compound in which a metal forms ionic bond with a non-metal and the metal can form more than one type of ions.
• Type-III: Compound in which a non-metal forms bond with a non-metal.

There is one another type of compound in which metal is bonded with a polyatomic ion

Rules for naming these compounds:

Type-I:

1. Name of metal cation is written as name of element.
2. Name of anion is written using root name and adding ‘ide’ to it.
3. Writing these names in the same sequence gives the name of compound.

Type-II:

1. Name of metal cation is written as name of element followed by charge carried by it in roman numerals in bracket.
2. Name of anion is written using root name and adding ‘ide’ to it.
3. Writing these names in the same sequence gives the name of compound.

Type-III:

1. The name of the first element is written as given in the periodic table.
2. Second element in anionic form and prefixes are used to denote the number of atoms. Like, prefix mono is not used for 1element.

When metal is bonded with polyatomic ion, rules are similar to ionic binary compounds.

Answer to Problem 2STP

D

Explanation of Solution

Iron(II) sulphide is compound of sulphide ion with metal of type-II. Suphide ion carry -2 charge. So, its formula is $FeS$ .

Sulphur hexafluoride is a binary compound of non-metal with non-metal. So, its formula is $S{F}_6$

Lead(IV) oxide is compound of oxide ion with metal of type-II. Oxide ion carries -2 charge. So, its formula is $Pb{O}_2$ .

Ammonium sulphate is a compound of polyatomic ion ammonium with polyatomic ion “sulphate”. Ammonium ion carries +1 charge and sulphate carries -2. Therefore, correct formula is ${\left(N{H}_4\right)}_{2}S{O}_4$

Conclusion

Applying the rules suggest all the compounds are named correctly except of ammonium sulphate. So option D is correct.