# Stoichiometry of Chemical Equations and Formulas.

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Stoichiometry of Chemical Equations and Formulas

Chemical Equations A statement in formulas that expresses the identities and quantities of the substances involved in a chemical or physical change.

Types of Chemical Reactions 1. __________________ Reaction – multiple reactants combine to form one product. H 2 + O 2  H 2 O

2. __________________ Reaction – one reactant breaks down into multiple products. H 2 O  O 2 + H 2

3. __________________ Reaction – a single element reacts with a compound to form a new single element and a new compound. NaBr + Cl 2  NaCl + Br 2

4. __________________ Reaction – 2 compounds react to form 2 new compounds. AgNO 3 + NaCl  NaNO 3 + AgCl

5. __________________ Reaction – a hydrocarbon reacts in the presence of oxygen to form either (a) CO 2 and H 2 O or; (b) CO and H 2 O –Combustion reaction products are dependent on the amount of oxygen present to react. Excess amount of oxygen, CO 2 and H 2 O are produced. Limited amount of oxygen, CO and H 2 O are produced.

In chemical equations, atoms cannot be created, changed, or destroyed, only rearranged into different combinations.

____________  ____________

1. Translate the equation. 2. Balance the atoms –Atoms must be the same on both sides – both identity and quantity.

Mg + O 2  MgO Reactants Product Mg – 1 Mg - 1 O – 2 O - 1 Must balance the oxygen atoms, which will change the magnesium atoms.

H 2 + O 2  H 2 O CH 4 + O 2  CO 2 + H 2 O

What is Stoichiometry __________________ nature of chemical formulas and chemical reactions. Allows you to determine how much of a __________________ will be formed from the known __________________. Allows you to determine how much of a __________________ is needed for the reaction to run to completion.

Quantitative analysis using chemical equations. Grams Reactant Moles Reactant Moles Product (mole to mole ratio from balanced equation) Grams Product New Step

Mole Ratio This comes from a __________________. The __________________ in the balanced equation determine the mole ratio of one substance to another substance. Anytime you are changing from one substance to a totally new substance, you must use a __________________ from the balanced equation.

1. Set up the given. 2. Change grams of given to moles of given. 3. Mole to mole conversion. 4. Change moles of what you are looking for to grams.

Theoretical Yield The __________________ of product that is calculated to form. Actual Yield – amount of product actually obtained in a reaction Percent Yield – relates the actual yield to the theoretical yield. –(Theoretical Yield – Actual Yield) X 100 Theoretical Yield

Limiting Reagent Occurs when you have a __________ amount of a reactant. The __________________ will stop forming when the ___________________________ is used up.

Limiting Reagent When given two quantities of ___________________, you must first determine which reactant is the __________________________. Again, the limiting reagent is the one that will yield the _____________ amount of ___________________.

Limiting Reagent To determine which reactant is the ______________________, you must first determine how much of one reactant will react with the other reactant. If you do not have enough, that is the ___________________ reagent. If you have too much, that is the reagent in _______________.

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