Chemical Reactions Chapter 10

Chemical reaction =process by which the atoms of one or more substances rearrange to form different substances.

Law of Conservation of Mass: Mass is not created or destroyed in a Chemical Reaction

Evidence of a chemical reaction 1)Release of energy in the form of heat or light (exothermic reaction) 2) Absorption of energy (endothermic reaction)

Evidence of a chemical reaction 3) Color change

Evidence of a chemical reaction 4) Appearance of a solid 5) Appearance of bubbles 6) Odor

Chemical Equations 1)Reactants  Products 2)Symbols: (s) solid state (l)liquid state (g)gaseous state (aq) aqueous = water solution Example:

Writing skeleton equations Liquid carbon disulfide reacts with oxygen gas, producing carbon dioxide gas and sulfur dioxide gas Solid zinc and aqueous hydrogen sulfate react to produce hydrogen gas and aqueous zinc sulfate

Writing skeleton equations Hydrogen (g) + bromine (g)  hydrogen bromide (g) Carbon monoxide(g) + oxygen(g)  carbon dioxide (g)

Writing skeleton equations Iron (s) + chlorine (g)  iron III chloride (s) Carbon (s) + sulfur (s)  carbon disulfide (l)

Reading a chemical equation

Reading a chemical equation with Coefficients

Balancing a chemical equation: 1) Write the skeleton equation for a reaction. 2) Change the coefficients until the number of atoms of each element are equal on both sides of the equation. 3) Make sure the coefficients are in their lowest ratio.

Balance the equation ___ C (s) + ___ S (s)  ___ CS 2 (l) ___ Fe (s) + ___Cl 2 (g)  ___ FeCl 3 (s)

Balance the equation __ CH 4 (g) +__ O 2 (g)  __CO 2 (g) +__H 2 O(g) __C 2 H 6 (g) +__ O 2 (g)  __CO 2 (g) +__H 2 O(g)

Balance the equation __K 2 CrO 4 (aq) + ___Pb(NO 3 ) 2 (aq)  ___KNO 3 (aq) + ___PbCrO 4 (s) ___Fe (s) + ___Sn(NO 3 ) 4 (aq)  ___Fe(NO 3 ) 3 (aq) + ___ Sn (s)