# Chemical Equation A shorthand way of reporting details

• Slides: 7

Chemical Equation • A shorthand way of reporting details of a chemical reaction • Reactants – The starting substances in a reaction – Placed on the left side of the equation • Products – The substances formed during a chemical reaction – Placed on the right side of the equation • Arrow is read as yields Episode 604

Coefficients • Used to balance equation • Represent the number of molecules, formula units, or atoms of the substances. http: //www. youtube. com/watch? v=x 9 i. Zq 3 Zxb. O 8&feature=related • Law of Conservation of Mass – Mass cannot be created or destroyed. Zn + 2 HCl → Zn. Cl 2 + H 2 Episode 604

2 H 2 + O 2 → 2 H 2 O 2 • Cannot add or change subscripts • Draw boxes C 3 H 8 + 5 O 2 → 3 CO 2 C=3 H=8 O = 2 10 + 4 H 2 O C=1 3 H=28 O = 3 7 10 Episode 604

Guidelines for Balancing Equations • Start by making an element inventory • Draw boxes around each formula in the equation • Begin with one molecule or formula unit of the substance containing the most atoms • Balance polyatomic ions that appear on both sides of the equation as a single unit – Appears in a reactant and a product • Balance hydrogen and oxygen atoms last Episode 604

Polyatomic Ions? Cu + 2 Ag. NO 3 → Cu(NO 3)2 + Cu = 1 Ag = 1 2 NO 3 = 1 2 2 KNO 3 → K=1 2 N=1 2 O=3 6 2 Ag Cu = 1 Ag = 1 2 NO 3 = 2 2 KNO 2 + O 2 K=1 2 N=1 2 O=4 6 Episode 604

Hydrogen and oxygen combine to produce water H + O → H 2 O • Reasonable…? Balan ce it ! • But, wrong 2 H 2 + O 2 → 2 H 2 O • 7 Diatomic Elements – Diatomic: two elements – Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine Episode 604

O 2 Carbon. CS disulfide reacts with oxygen 2 to produce carbon and COdioxide 2 sulfur dioxide. Ba SO la 2 nce CS 2 + 3 O 2 → C=1 S=2 O=2 6 it ! CO 2 + 2 SO 2 C=1 S=1 2 O=46 Episode 604