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Section 2.6—Chemical Reactions

Section 2.6—Chemical Reactions. If we’re going to do chemical reactions with antacids, we’d better know how to write them!. Diatomic Molecules. This is not in the notes so you should pay attention, and add it in!!!!!!.

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Section 2.6—Chemical Reactions

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  1. Section 2.6—Chemical Reactions If we’re going to do chemical reactions with antacids, we’d better know how to write them!

  2. Diatomic Molecules This is not in the notes so you should pay attention, and add it in!!!!!! Some elements are so chemically reactive that, when they are not bonded to any other elements, they find another atom of their same kind to bond with.

  3. Diatomic Molecules To write a formula for a diatomic molecule you write the symbol of the element and use a two as a subscript. Which elements form diatomic molecules? Well, I am glad you asked!

  4. Diatomic Molecules There are seven diatomic molecules:

  5. Diatomic Molecules There are two good ways to remember the diatomic molecules First – Remember a funny word! HOFBrINCl

  6. Diatomic Molecules Second – Remember a funny phrase: The six that make a seven plus hydrogen.

  7. Now back to our regularly scheduled notes.

  8. O O H H H H Chemical Reactions Bonds and atoms are rearranged to form new compounds. 2 H2 + O2 2 H2O Watch as 2 H2 and 1 O2 undergo a chemical reaction

  9. O O H H H H O O H H H H Chemical Reactions Bonds and atoms are rearranged to form new compounds. 2 H2 + O2 2 H2O The compounds in the end are different from those in the beginning Bonds are broken and formed between different atoms

  10. Chemical Equations The “sentence” of chemistry that shows how the starting materials and the final products of a chemical reaction

  11. Formula equation: Mg (s) + 2 HCl (aq) MgCl2 (aq) + H2 (g) Examples of Chemical Equations Word equation: magnesium metal is reacted with aqueous hydrochloric acid to produce aqueous magnesium chloride and hydrogen gas  Visualization

  12. Parts of a Chemical Equation The starting materials for the reaction—each compound is separated by a “+” Formed in the reaction Products Reactants NaCl (aq) + AgNO3 (aq)  AgCl(s) + NaNO3 (aq) States of matter Arrow Read as: Yields Produces Forms Makes etc. s = solid l = liquid g = gas aq = aqueous (dissolved in water)

  13. Writing Chemical Equations • You must write each chemical formula correctly first! (Section 2.2) • “and”, “is mixed with” or “reacts with” = + • “yield”, “produces” and “forms” =  We will learn to balance equations in the next section, so don’t worry about it now!

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

  15. Let’s Practice #1 Aluminum metal is reacted with hydrochloric acid to form aluminum chloride and hydrogen gas Example: Write the word equation into symbol form Al + HCl  AlCl3 + H2

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

  17. Let’s Practice #2 Copper (II) nitrate and sodium hydroxide form copper (II) hydroxide and sodium nitrate Example: Write the word equation into symbol form Cu(NO3)2 + NaOH  Cu(OH)2 + NaNO3

  18. Cl Ag Na N N Na O Cl O O O O O Ag Double Replacement Reactions The cations from two compounds replace each other. NaCl + AgNO3 AgCl + NaNO3 Two ionic compounds switch ions

  19. Double Replacement Reactions General format of a double replacement reaction:

  20. Products of a Double Replacement 1 Combine the cation of the first reactant with the anion of the second reactant Ca Cl2 + Ag NO3

  21. Products of a Double Replacement 2 Combine the cation of the second reactant with the anion of the first reactant Ca Cl2 + Ag NO3

  22. Products of a Double Replacement 3 Remember to write cations first … & balance charges with subscripts when writing formulas Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion! Ca Cl2 + Ag NO3 + + Ca Cl2 Ag NO3 Ca(NO3)2 AgCl

  23. 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

  24. Products of a Neutralization Reaction 1 Combine the cation of the first reactant with the anion of the second reactant H2 SO4 + Na OH

  25. Products of a Neutralization Reaction 2 Combine the cation of the second reactant with the anion of the first reactant H2 SO4 + Na OH

  26. Products of a Neutralization Reaction 3 Remember to write cations first … & balance charges with subscripts when writing formulas Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion! H2 SO4 + Na OH + + H2 SO4 Na OH Na2SO4 HOH You can write the water as “HOH” when you combine the cation & anion or you can change it to “H2O”

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

  28. Let’s Practice #3 Example: Write the products for this reaction Sr(OH)2 + HBr  SrBr2 + HOH

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

  30. Let’s Practice #4 Example: Write the products for this reaction HCl + Ca(OH)2 CaCl2 + HOH

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