Stoichiometry

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Stoichiometry - PowerPoint PPT Presentation

Stoichiometry. Balanced Equations. All stoichiometry problems start with a balanced equation. You must check for this! If it is not balanced, BALANCE IT!. Reviewing Balancing Equations. S. Fe. Fe 2 S 3. S. Fe. S. Can change coefficients but CANNOT change subscripts Example

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PowerPoint Slideshow about ' Stoichiometry' - hanh

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Stoichiometry

Balanced Equations
• You must check for this!
• If it is not balanced, BALANCE IT!
Reviewing Balancing Equations

S

Fe

Fe2S3

S

Fe

S

• Can change coefficients but CANNOT change subscripts
• Example
• 3S + 2 Fe  Fe2S3
Reviewing Balancing Equations
• Al + CuO Al2O3 + Cu
• ____________________________
Reviewing Balancing Equations
• H2 + O2 H2O

_______________________

Equations and the Mole
• Remember what an equation actually means
• Mg + S  MgS
• One _____________reacts with one ___________ creating one formula unit of MgS
• But
• This also means that one mole of _________ reacts with one mole of ___________ to form one mole of _______ formula units.
• 1 mol Mg, 1 mol S, and 1 mol MgS are stoichiometry equivalents
Equations and the Mole (cont)
• C3H8 + 5O2 3CO2 + 4H2O
• Now, ____ mol C3H8, _____ mol O2, _____ mol CO2, and _______ mol H2O are stoichiometry equivalents
What does this mean?
• As stoichiometry equivalents, they can be used in a conversion factor
• __________________ Conversion Factors
• One equivalent is placed on top and one on bottom
• Allows us to move from one compound to another in a balanced equation
Stoichiometry Problems

Given the equation:

MgCl2 + 2 AgNO3 Mg(NO3)2 + 2 AgCl

What is the mass of AgCl produced if 24g of MgCl2 is reacted with excess AgNO3?

What amount of MgCl2 will react with 3.85 g AgNO3?

Limiting Reagents
• So far we have been assuming that we have an excess of all the other reactants
• This is not often true….often you have a set amount of both reactants
• Each amount would lead you to a different amount of product
• Must use the number that is ___________
Limiting Reagent Problem

Given the equation:

MgCl2 + 2 AgNO3 Mg(NO3)2 + 2 AgCl

How much AgCl will be produced if 28g of MgCl2 is reacted with 51g of AgNO3?

Theoretical and Actual Yield
• Yield is the amount of product that you get from a reaction
• Theoretical yield is the amount that you should get based on using stoichiometry
• Actual yield is the amount of product actually attained during an experiment
% Yield
• Calculated by taking
• _____________________________________
Theoretical and % Yield

Given the equation:

MgCl2 + 2 AgNO3 Mg(NO3)2 + 2 AgCl

What is the percent yield of Mg(NO3)2 if 168.4 g of AgNO3 is reacted to produce 47.2g of Mg(NO3)2?