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Introduction to Chemical equations

Introduction to Chemical equations. Unit 5. Chemical Reactions. A chemical reaction is a change in which one or more substances are converted into new substances Review: a substance is an element or a compound. The reactants are the substances that exist before the reaction.

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Introduction to Chemical equations

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  1. Introduction to Chemical equations Unit 5

  2. Chemical Reactions A chemical reaction is a change in which one or more substances are converted into new substances Review: a substance is an element or a compound

  3. The reactants are the substances that exist before the reaction The productsare the substances that exist after the reaction Chemical Reactions

  4. Conservation of Mass Law of Conservation of Mass: The total mass of the products must always equal the mass of the reactants Mercury (II) oxide = oxygen + mercury 10.0g = 0.7g + 9.3g

  5. A chemical equationdescribes the chemical reaction using formulas and symbols (and usually coefficients) Ca + O2→CaO Chemical Reactions

  6. Seven elements are always written as two atoms bonded together! When writing chemical equations, you will always write these elements with a subscript of a ‘2’ Br2 I2 N2 Cl2 H2 O2 F2 DIAtomic elements!

  7. Chemical Reaction Symbols Coefficient Yields Subscript

  8. Symbols for State Solids: (s) Liquids: (l) Dissolved in water: (aq) Gases: (g) Chemical Equation Symbols 2 Mg (s) + O2 (g) → 2 MgO (s)

  9. Coefficients represent the number of units of each substance that take part in the reaction Chemical Equations Al +       O2      Al2O3

  10. Because mass must be conserved, coefficients are used to balance an equation The same number of atoms of each element must be on both sides of the equation Chemical Equations 4 Al + 3 O22 Al2O3

  11. Balancing Chemical Equations Trial and Error Method! Cu + O2 → Cu2O Al + O2 → Al2O3

  12. Balancing Chemical Equations N2 + H2 → NH3 • Mg + P4 → Mg3P2

  13. Balancing Chemical Equations Al(OH)3 + HBr AlBr3 + HOH

  14. Balancing Chemical Equations NH4OH + H3PO4 (NH4)3PO4 + HOH

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