Intro to Unit 9 - naming, balancing, conversions

Unit 9 Introduction

Review of naming, balancing, and the mole

Part I: Writing Formulas

Remember to find charges and criss cross all ionic compounds.

Do NOT use charges, but use prefixes and do NOT criss cross for all covalent compounds.

Don't forget you still need to know polyatomic ions!

• Find the charges on the periodic table.

• Cross them to find the subscripts.

• Like charges reduce and cancel.

• When a transition metal is followed by a roman numeral, the roman numeral is the charge. It must still be criss crossed.

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​Criss cross charges for ionic compounds.

Multiple Choice

What is the formula for magnesium chloride?

• MgCl

• Mg₂Cl

• MgCl₂

• Mg(ClO₃)₂

Multiple Choice

The chemical formula for an ionic compound of potassium and oxygen is

• KO.

• K₂O.

• K₂O₂.

• KO₂.

Multiple Choice

The chemical formula of magnesium hydroxide is

• MgOH₂

• Mg(OH)₂

• Mg(OH)

• MgH₂

Multiple Choice

Aluminum fluoride is...

• AlF₃

• Al₃F

• FAl₃

• F₃Al

Multiple Choice

The chemical formula of Iron (III) bromide is

• FeBr

• Fe(III)Br

• FeBr₃

• Fe₂Br₃

• Fe₃Br

Multiple Choice

The correct chemical formula for magnesium phosphide is

• MgP

• Mg₂P₃

• Mg₃P₂

• Mg₃(PO₄)₂

Multiple Choice

The chemical compound for sodium phosphate would be:

• Na(PO₄)

• Na₂(PO₄)

• Na₃(PO₄)

• Na(PO₄)₃

Multiple Choice

What is the formula for manganese(III) oxide?

• Mn₃O

• Mn₃O₂

• MnO

• Mn₂O₃

• MnO₂

• Do NOT criss cross.

• Do NOT use charges.

• The prefix indicates the subscript

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​Use prefixes for covalent compounds.

Multiple Choice

phosphorus trichloride

• P₁Cl₃

• PCl₃

• K₃Cl

• P₃Cl

Multiple Choice

diphosphorus pentoxide

• P₂O₅

• PO₅

• P₅O₂

• P₂O₆

Multiple Choice

The chemical formula of sulfur hexabromide is

• SBr₆

• S₆Br

• S(VI)Br

• S6Br

Multiple Choice

The chemical formula of dinitrogen textroxide is

• Ni₂O₄

• NiO

• N₂O₄

• NiO₂

Multiple Choice

Which of the following will you NEVER see in covalent compounds?

• prefixes

• subscripts

• roman numerals

• nonmetals

Multiple Choice

What is the name of C₃Cl₈ ?

• Carbon octachloride

• Tricarbon octachloride

• Carbon trichloride

• Octacarbon trichloride

Part II: Balancing

Count the number of each individual atom on each side of the reaction.

Can only change the coefficients, not the formulas.

Try to balance the equations shown below.

We will go over these together as a class!

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Practice!

Multiple Choice

 Mg  +  ___ HCl  →   MgCl₂  +   H₂

• 1

• 2

• 3

• 4

Multiple Choice

Balance this equation
_Al +_HCl --> _H₂ +_AlCl₃

• 2, 6, 3, 2

• it is already balanced

• 4, 12, 3, 4

• 2, 1, 4, 5

Balance the elements in a specific order: H, C, O

The number in front of water must be even!

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Balancing Combustion Reactions

Part III: Molar Mass

Include all atoms of each element when calculating the molar mass.

Round to two decimal places.

Ca: 1 (40.08 g)

F: 2 (19.00 g)

= 78.08 g CaF₂

CaF₂

Molar Mass Examples:

(NH₄)₂O

N: 2 (14.01 g)

H: 8 (1.01 g)

O: 1 (16.00 g)

= 52.108 g (NH₄)₂O

Multiple Choice

What is the molar mass of Cu(OH)₂?

• 97.57

• 81.57

• 80.56

• 161.12

Part IV: Conversions

Identify given & unknown.

Set up the units first.

Plug in the proper conversion factor.

SOLVE!

• Units that are directly connected can be converted in one step

• Units that are not will need additional steps to convert!

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​Use conversion factors to convert one unit to another.

Try the problems above. Show your work.

Answers:

224.68 g Fe(OH)₂

2.20 x 10²⁴ atoms Si

Practice!

Great job with the review!

​Unit 9 (stoichiometry) is a combination of units 7 & 8. You will need to be able to write out an equation, balance it, and then use the coefficients to do conversions. If you are struggling with these topics, please come see me ASAP.