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Chapter 9 Chemical Reactions
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Chemical reaction process by which the atoms of one or more substances are rearranged to form different substances same as chemical change
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Chemical reaction starting substances are reactants substances formed or produced during reaction are products
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Evidence of a chemical reaction (change)
1. temperature change 2. color change production of a gas (odor/bubbles) 4. formation of a solid (precipitate)
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Chemical equation A statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction.
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Silver metal reacts with
hydrogen sulfide gas in the air to form solid silver sulfide and hydrogen gas.
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Some pure elements exist as diatomic molecules.
H2, N2, O2, F2, Cl2, Br2, I2
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-gens hydrogen oxygen nitrogen halogens (group 17)
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Write formulas / symbols for the following:
magnesium nitrogen carbon dioxide fluorine sodium chloride sulfur
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Law of Conservation of Mass
Mass is neither created nor destroyed during a chemical reaction – it is conserved. Total mass of reactants always equals total mass of products.
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Therefore, chemical equations must be balanced; same number of atoms of each element on each side of arrow.
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To balance a chemical equation:
Count number of atoms of each element on each side of arrow.
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Add coefficients in front of formulas. Must be lowest whole number ratio.
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Iron metal reacts with oxygen gas to form iron(III) oxide (rust.)
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Classifying chemical reactions
useful for understanding chemical reactions and for predicting products five general types of reactions
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Synthesis reactions two or more substances react to form a single product A + B AB Key: one product
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Synthesis reaction Zinc metal reacts with solid iodine to form solid zinc iodide.
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Decomposition reactions
a single compound breaks down into two or more simpler substances (elements or compounds) AB A + B Key: one reactant
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Decomposition reactions
often must add energy (heat/electricity) to make reaction occur
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Decomposition reaction
When heated, solid potassium chlorate reacts to form solid potassium chloride and oxygen gas.
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Single-replacement reactions
one element replaces another element in a compound A + BX AX + B
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Single-replacement reactions
more active element replaces less active element
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When balancing replacement reactions: keep polyatomic ions intact and write water as HOH (hydrogen and a hydroxide.)
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Single-replacement reaction
Copper metal reacts with aqueous silver nitrate to produce silver metal and aqueous copper(II) nitrate. copper replaces silver
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Single-replacement reaction
Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.
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Double-replacement reactions
Exchange of ions between aqueous solutions of two compounds. AX + BY AY + BX
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Double-replacement reactions
Aqueous solutions of lead(II) nitrate and potassium iodide react to form aqueous potassium nitrate and a precipitate of lead(II) iodide.
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Combustion reactions substance reacts rapidly with oxygen gas and releases energy in form of heat and light may also be synthesis reaction
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Iron metal reacts with oxygen gas to form iron(III) oxide (rust.)
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Iron metal burns in oxygen gas to form iron(III) oxide.
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Combustion reactions If reactant contains carbon, then products of a combustion reaction are always carbon dioxide gas and water vapor.
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Sucrose (C12H22O11) burns in oxygen.
Products are carbon dioxide gas and water vapor.
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Single-replacement reactions
more active element replaces less active element
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A more active metal will replace a less active metal.
Will the following single-replacement reaction occur? Fe(s) + Cu(NO3)2(aq) Yes, iron is more active than copper.
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Fe(s) + Cu(NO3)2(aq) Cu(s) + Fe(NO3)2(aq)
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A more active nonmetal will replace a less active nonmetal.
Will the following single-replacement reaction occur? Cl2(g) + NaBr(aq) Yes, chlorine is more active than bromine.
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Cl2(g) + 2NaBr(aq) Br2(g) + 2NaCl(aq)
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Will the following single-replacement reaction occur?
Al(s) + MgCl2(aq) No, aluminum is not more active than magnesium.
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Solid calcium metal reacts with water to produce aqueous calcium hydroxide and hydrogen gas.
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When aqueous solutions
of sulfuric acid and barium chloride are mixed, a precipitate of barium sulfate and aqueous hydrochloric acid are formed.
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