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Chemical Reactions and Stoichiometry. Chapters 7 through 9. Chemical Equations. Equations describe a chemical reaction (change) Original materials (reactants) change into new materials (products) Usually involves some observable change in properties. Reactants. “Yields”. Products.
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Chemical Reactions and Stoichiometry Chapters 7 through 9
Chemical Equations • Equations describe a chemical reaction (change) • Original materials (reactants) change into new materials (products) • Usually involves some observable change in properties
Reactants “Yields” Products Subscripts show mole ratio within each compound Coefficientsshow how many (moles) of each compound State Symbolss - solid l - liquid g - gas aq - aqueous CaCO3(s) + 2 HCl(aq) CaCl2(aq) + H2O(l) +CO2(g) One mole of solid calcium carbonate reacts with two moles of aqueous hydrochloric acid to yield one mole of aqueous calcium chloride, one mole of liquid water and one mole of carbon dioxide gas.
Balancing Chemical Equations • Law of Conservation of Mass - in a normal chemical reaction matter is not created or destroyed • components can only be re-arranged • if there are two carbons in the reactants, there must be two carbons in the products • 2 H2O2(aq) 2 H2O(l) + O2(g) 4 H 4 H 4 O 2 O + 2 O
Balance using COEFFICIENTS ONLY Example: __ AgNO3(aq) + __ CaCl2(aq) __ AgCl(s) + __ Ca(NO3)2(aq) • Balance one element at a time • Double check when you are done
Try one: __ MnO2(s) + __ Mg(s) __ Mn(s) + __ MgO(s) • Try another: __ C2H5OH(l) + __ O2(g) __ CO2(g) + __ H2O(l)
Balance the Following: ___ KNO3(s) ___ KNO2(s) + ___O2(g) ___ RbBr(aq) + ___ AgCl(s) ___ AgBr(s) + ___ RbCl(aq) ___ Zn(s) + ___ CrCl3(aq) ___ CrCl2(aq) + ___ ZnCl2(aq) ___ Fe(s) + ___ H2SO4(aq) ___ Fe2(SO4)3(aq) + ___ H2(g)
When solid copper(II) carbonate is heated, it yields solid copper(II) oxide and carbon dioxide gas. Write a balanced chemical equation for the reaction.