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Section 2.6—Chemical Reactions Objectives: Define the components of a chemical reaction Convert word equations to formula equations Define and predict.

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Presentation on theme: "Section 2.6—Chemical Reactions Objectives: Define the components of a chemical reaction Convert word equations to formula equations Define and predict."— Presentation transcript:

1 Section 2.6—Chemical Reactions Objectives: Define the components of a chemical reaction Convert word equations to formula equations Define and predict products for double replacement and neutralization reactions

2 Watch as 2 H 2 and 1 O 2 undergo a chemical reaction O O O O When substances react, bonds are broken, atoms are rearranged, and bond are re-formed to create new compounds. H H H H H H H H 2 H 2 + O 2  2 H 2 O Chemical Reactions

3 O O O O Bonds and atoms are rearranged to form new compounds. H H H H O O H H H H O O H H H H H H H H The substances in the end are different from those in the beginning. Bonds are broken and re-formed between different atoms 2 H 2 + O 2  2 H 2 O Chemical Reactions

4 In chemistry, the “sentence” (showing the starting materials and the final products of a chemical reaction) is called a chemical equation.

5 Examples of Chemical Equations Word equation: magnesium metal is reacted with aqueous hydrochloric acid to produce aqueous magnesium chloride and hydrogen gas Visualization Formula equation: Mg (s) + 2 HCl (aq) MgCl 2 (aq) + H 2 (g)

6 Parts of a Chemical Equation NaCl (aq) + AgNO 3 (aq)  AgCl(s) + NaNO 3 (aq) Reactants States of matter Arrow Products The starting materials for the reaction—each compound is separated by a “+” s = solid l = liquid g = gas aq = aqueous (dissolved in water) Read as: Yields Produces Forms Makes etc. Formed in the reaction

7 You must write each chemical formula correctly first! (Recall how to write formulas from names - Section 2.2) “and”, “is mixed with” or “reacts with” = + “yield”, “produces” and “forms” =  Then after they are written, chemical equations have to be balanced – we’ll do that in Sec. 2.7! Writing Chemical Equations

8 Let’s Practice #1 Example: Write the word equation into symbol form Aluminum metal is reacted with hydrochloric acid to form aluminum chloride and hydrogen gas

9 Let’s Practice #1 Al + HCl  AlCl 3 + H 2 Example: Write the word equation into symbol form

10 Let’s Practice #2 Example: Write the word equation into symbol form Copper (II) nitrate and sodium hydroxide form copper (II) hydroxide and sodium nitrate

11 Let’s Practice #2 Cu(NO 3 ) 2 + NaOH  Cu(OH) 2 + NaNO 3 Example: Write the word equation into symbol form

12 NaCl + AgNO 3  AgCl + NaNO 3 Double Replacement Reactions The cations from two compounds replace each other. Cl Na Ag O O O O N N O O Cl Ag Na O O O O N N O O Two ionic compounds switch ions

13 Double Replacement Reactions The general format of a double replacement reaction:

14 Combine the cation of the first reactant with the anion of the second reactant 1 Products of a Double Replacement CaCl 2 + AgNO 3 

15 Combine the cation of the second reactant with the anion of the first reactant 2 Products of a Double Replacement CaCl 2 + AgNO 3 

16 & balance charges with subscripts when writing formulas Remember to write cations first … AgCl CaCl 2 +AgNO 3 3 Ca(NO 3 ) 2 + CaCl 2 AgNO 3 + Products of a Double Replacement Remember NOT the change the subscripts that are part of any polyatomic ion!

17 Neutralization Reactions General format of a neutralization reaction: Neutralization reactions are double replacement reactions where one cation is “H” and one anion is “OH” and water is formed. ACID BASE IONIC WATER COMPOUND

18 Combine the cation of the first reactant (the acid) with the anion of the second reactant (the base). This gives you the water. 1 Products of a Neutralization Reaction H 2 SO 4 + NaOH 

19 Combine the cation of the second reactant with the anion of the first reactant. This gives you an ionic compound. 2 Products of a Neutralization Reaction H 2 SO 4 + NaOH 

20 & balance charges with subscripts when writing formulas Remember to write cations first … HOH H2H2 SO 4 +NaOH 3 Na 2 SO 4 + H2H2 SO 4 NaOH + Products of a Neutralization Reaction Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion! You can write the water as “HOH” when you combine the cation & anion or you can change it to “H 2 O”

21 Let’s Practice #3 Example: Write the products for this reaction Sr(OH) 2 + HBr 

22 Let’s Practice #3 SrBr 2 + HOH Example: Write the products for this reaction Sr(OH) 2 + HBr 

23 Let’s Practice #4 Example: Write the products for this reaction HCl + Ca(OH) 2 

24 Let’s Practice #4 CaCl 2 + HOH Example: Write the products for this reaction HCl + Ca(OH) 2 


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