Chemistry 9th Chap 6 : Topic 4 - Maryam Publications

Chemistry Chapter 6 : Topic 4

Binary Ionic Formulae

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An element X forms a cation with a + 2 charge, while element Y forms an anion with a - 1 charge. What will be the correct formula of the compound formed between X and Y ?

A) XY

B) X₂Y

C) XY₂

D) X₂Y₃

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Which of the following formulas is correctly derived from Al³⁺ and O²⁻ ions?

A) Al₂O₃

B) AlO₃

C) Al₃O₂

D) AlO

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A student writes the formula of magnesium chloride as MgCl. What is the conceptual mistake?

A) Ignoring valency of magnesium

B) Writing charges incorrectly

C) Ignoring valency of chlorine

D) Not balancing charges between Mg²⁺ and Cl⁻

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Which of the following correctly represents the compound formed between Ca²⁺ and N³⁻ ions?

A) CaN₂

B) Ca₂N₃

C) CaN

D) Ca₃N₂

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The formula FeCl₃ indicates which of the following about iron?

A) Iron forms + 2 ion

B) Iron forms + 3 ion

C) Iron forms + 1 ion

D) Iron forms - 3 ion

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Which rule is essential while writing formulas of binary ionic compounds?

A) Charges must be balanced

B) Only metal valency is considered

C) Charges must be ignored

D) Charges must be added

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A compound has formula Na₂O. What does this indicate?

A) Both have + 1 charge

B) Oxygen has + 2 charge

C) Sodium has - 2 charge

D) Sodium has + 1 and oxygen - 2 charge

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Which of the following is correctly named?

A) Al₂O₃ ⟹ Dialuminium trioxide

B) CaCl₂ ⟹ Calcium dichloride

C) MgO ⟹ Magnesium oxide

D) NaCl ⟹ Sodium monochloride

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What will be the formula of a compound formed between K⁺ and S²⁻?

A) K₂S

B) KS

C) K₂S₂

D) KS₂

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Which of the following represents a correct ionic formula and name pair?

A) CaO ⟹ Calcium monoxide

B) Na₂O ⟹ Sodium dioxide

C) K₂S ⟹ Dipotassium sulfide

D) MgCl₂ ⟹ Magnesium chloride

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Why are subscripts used in writing ionic formulas?

A) To show atomic masses

B) To represent number of molecules

C) To indicate physical state

D) To balance electrical charges

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Which compound is correctly formed from Fe²⁺ and O²⁻?

A) FeO

B) FeO₂

C) Fe₂O

D) Fe₂O₂

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If an element forms a + 3 ion, how many - 1 ions are required to balance it?

A) 3

B) 1

C) 2

D) 4

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Which of the following is incorrectly written formula?

A) Na₂O

B) CaCl₂

C) Mg₂Cl

D) Al₂O₃

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The formula Ba₃N₂ shows that:

A) Nitrogen has + 3 charge

B) Barium is + 2 and nitrogen is - 3

C) Both have same charges

D) Barium has - 2 charge

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Which step is performed first while writing an ionic compound formula?

A) Naming compound

B) Writing subscripts

C) Balancing charges

D) Writing symbols of ions

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A compound contains Al³⁺ and Cl⁻ ions. Which reasoning explains the formula AlCl₃?

A) Chlorine has + 3 charge

B) Charges cancel by 1 :3 ratio

C) Aluminium has - 3 charge

D) Equal number of ions

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Which of the following compounds has simplest ratio of ions?

A) NaCl

B) Al₂O₃

C) CaCl₂

D) Mg₃N₂

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Why is MgO written instead of Mg₂O₂?

A) To reduce atoms

B) To match atomic masses

C) Simplest whole number ratio

D) Molecular formula rule

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Which compound represents correct charge balance?

A) AlCl₃

B) Na₂Cl

C) Ca₂O

D) MgCl

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What will be the formula of lithium oxide?

A) LiO

B) LiO₂

C) Li₂O

D) Li₂O₂

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Which of the following requires criss-cross method?

A) Mg²⁺ and O²⁻

B) Na⁺ and Cl⁻

C) K⁺ and Br⁻

D) Al³⁺ and O²⁻

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Which is correct formula for zinc nitride (Zn²⁺and N³⁻)?

A) Zn₂N₃

B) ZnN

C) Zn₃N₂

D) ZnN₂

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What is the name of CaO?

A) Calcium oxide

B) Calcium oxygen

C) Calcium dioxide

D) Calcium monoxide

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Which statement best explains why ionic compounds are electrically neutral?

A) They have no charges.

B) They contain equal number of ions.

C) They contain equal number of atoms.

D) Total positive and negative charges cancel.

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