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Chemical Reactions

Chemical Reactions. Chemical Reactions. 10.1 Reactions and Equations Evidence of Chemical Reactions . The process of which the atoms of one or more substances are rearranged to form different substances is called a Chemical Reaction . Evidence of a Chemical Reaction 1 . color change

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Chemical Reactions

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  1. Chemical Reactions

  2. Chemical Reactions • 10.1 Reactions and Equations • Evidence of Chemical Reactions. • The process of which the atoms of one or more substances are rearranged to form different substances is called a Chemical Reaction. • Evidence of a Chemical Reaction • 1. color change • 2. formation of a solid (including smoke), liquid or gas • 3. energy is released or absorbed (temp change), also gives off light, noise • 4. odor

  3. Representing Chemical Reactions • Chemical Equations- are statements that chemists use to represent chemical reactions • They show: • Reactants- the starting substances • Products- the substances formed during a reaction

  4. Symbols • Chemical equations show the direction in which a reaction takes place, so, an arrow is used rather than an equals sign. You read the arrow as “react to produce” or “yield”.

  5. Word Equations • Word equations describe the reactants and products of chemical reactions. • Ex. reactant1 + reactant 2  product 1 • iron(s) + chlorine(g)  iron(III) chloride(s) • This equation is read: iron and chlorine react to produce iron(III)chloride

  6. Skeleton Equations • A skeleton equation uses chemical formulas rather than words to identify the reactants and the products. • Ex:iron(s) + chlorine(g)  iron(III) chloride(s) • Fe(s) + Cl2(g) FeCl3 (s)

  7. Writing Ionic Compound Formulas • Review. • 1. Write the symbols • 2. Write the charges • 3. Cross the charges from top to bottom. • 4. Remove the charges • 5. Simplify the numbers (ratios) and remove the ones. • Reminder: treat polyatomic ions as one ion.

  8. Balancing Chemical Equations. The law of conservation of matter states that, in a chemical change, matter is neither created nor destroyed.

  9. Balancing Chemical Equations. Chemical equations must show that matter is conserved during a chemical reaction. Such an equation is called a balanced equation.

  10. Balancing Chemical Equations. To balance an equation you must find the correct coefficients for the chemical formulas in the skeletal equations. A coefficientin a chemical equation is the number written in front of a reactant or product.

  11. Balancing Chemical Equations. Coefficients are whole numbers and are not written if the value is 1. In a balanced equation, coefficient is the lowest whole-number ratio of the amounts of all the reactants and products.

  12. Steps for Balancing Equations • 1. Write the skeletal equation for the reaction. • 2. Count the atoms of the elements in the reactants. • 3. Count the elements in the products. • 4. Change the coefficients to make the number of atoms of each element equal on both • sides of the equation. • 5. Write the coefficients in their lowest possible ratio. • 6. Check your work.

  13. Steps for Balancing Equations • 1. Write the skeletal equation for the reaction.

  14. Steps for Balancing Equations • 2. Count the atoms of the elements in the reactants.

  15. Steps for Balancing Equations • 3. Count the elements in the products.

  16. Steps for Balancing Equations • 4. Change the coefficients to make the number of atoms of each element equal on both

  17. Steps for Balancing Equations • 5. Write the coefficients in their lowest possible ratio. • Ratio is 1:1:2; so it is the lowest possible ratio

  18. Steps for Balancing Equations • 6. Check your work. • Make sure the chemical formulas are written correctly. • Check that the number of atoms is equal on both sides.

  19. Recommended order of balancing • 1. Metals • 2. Non-metals • 3. Polyatomic ions • 4 Oxygen and hydrogen • MgCl2+ Na2O  MgO + NaCl

  20. Try to balance these equations!

  21. Do Now • In your packet: Write a skeletal equation of the following reactions and then balance.

  22. FeCl3(aq) + 3NaOH  Fe(OH)3(s) + 3NaCl(aq) • CS2(L) + 3O2(g)  CO2(g) + 2SO2(g) • Zn(s) + H2SO4(aq)  H2(g) + ZnSO4(aq)

  23. Classifying Chemical Reactions Synthesis Reaction • When two elements or substances react it is always a synthesis reaction. • A + B AB

  24. Synthesis Reaction

  25. Classifying Chemical Reactions Combustion Reaction • In combustion reactions, oxygen combines with a substance and releases energy in the form of heat and light. • Ex

  26. Decomposition Reactions • A decomposition reaction is one in which a single compound breaks down into two or more compounds or elements. • AB  A + B

  27. Decomposition Reactions • AB  A + B • Decomposition reactions often require an energy source such as heat or electricity, to occur.

  28. Replacement Reactions Single Replacement Reactions • In a single-replacement reaction, the atoms of one element replace the atoms of another element in a compound. • A + BX  AX + B

  29. Replacement Reactions • Single Replacement Reactions • A + BX  AX + B

  30. Replacement Reactions • Single Replacement Reactions • A + BX  AX + B

  31. You can use the Activity Series Chart to predict if a single replacement reaction will occur. • A specific metal can replace any metal listed below it. • It cannot replace any metal listed above it.

  32. Single Replacement Reactions

  33. Replacement Reactions • Double Replacement Reaction • In a double replacement reaction ions are exchanges between two compounds.

  34. Replacement Reactions

  35. A solid produced during a chemical reaction is called a precipitate. • A double replacement reaction will produce either a precipitate, a gas, or water. • You can predict which ions will form a precipitate by using a solubility table.

  36. Classifying Chemical Equations __B__1. A + B  AB a. Decomposition Reaction __C__2. A + BX  B + AX b. Synthesis Reaction __D__3. AX + BY  AY + BX c. Single Replacement Reaction __E__4. CxHy+ O2 CO2 + H2O d. Double Replacement Reaction __A__5. AB  A + B e.Combustion Reaction

  37. Types of Reactionshttp://www.youtube.com/watch?v=tE4668aarckhttp://www.youtube.com/watch?v=aAWcCQB75d0 Do Now Synthesis Reaction1. CO2 C + O2 A + B AB 2. CH4+ O2 CO2 + 2H2O • Decomposition Reactions 3. NaCl+ AgNO3AgCl + NaNO3 AB  A + B 4. S + Cl2SCl2 • Combustion Reaction 5. Zn + 2HCl  ZnCl2 + H2 Replacement Reactions • Single Replacement • A + BX  AX + B • Double replacement • AX + BY  AY + BX

  38. 27. synthesis, combustion, decomposition, single replacement, double replacement. • 28. Oxygen combines with a substance and releases energy in the form of heat and light. • 29. In a single replacement reaction, atoms of one element replace atoms of another element in a compound. In a double replacement reaction two compounds dissolved in water exchange positive ions.

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