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WRITING CHEMICAL EQUATIONS REVIEW: 1. Evidence of a chemical reaction includes: 4. 2. 5. 3. The Law of Conservation of Mass/Matter states: BASICS ABOUT WRITING EQUATIONS: Chemical formulas (of elements, covalent compounds, acids, ionic compounds, bases, etc.) show chemistry at a standstill. Chemical equations show chemistry in action. The general formula for a chemical equation is: There may be one or more reactants and one or more products. Equations always tell us 3 things: 1. 2. 3. Two important principles to remember: 1. Every chemical compound has a formula which cannot be altered. If the formula is altered, you now have a new chemical with a new chemical composition and new chemical and physical properties. 2. A chemical reaction must account for every atom that is used. No atom can ever go unaccounted for in a chemical equation. What law is this an application of? SPECIFICS ABOUT WRITING CHEMICAL EQUATIONS: 1. There are seven elements that are diatomic when they stand alone. Always include the subscript 2 when they are by themselves. They are: Also, sulfur can naturally exist as and phosphorous can naturally exist as 2. means “yields” or “produces” or “forms” and shows the direction of the reaction. It means that the reaction goes to completion, or until the reactants are used up. 3. or or shows that the reaction is reversible and can proceed in either direction until it reaches equilibrium. Both reactants and products are present at all times once the reaction has begun. 4. or above the arrow shows that heat has been added. 5. A chemical written above the arrow shows that it is a the reaction, but isn’t produced or consumed. 6. . It speeds up is placed between all formulas on each side of the arrow. 7. These symbols written as subscripts following the formulas mean: (s) (l) (g) (aq) BALANCING CHEMICAL EQUATIONS: 1. Before beginning to balance an equation, check each to ensure that it is correct. can NOT be altered IN ANY WAY once you begin balancing an equation. 2. The law of states the same number of each atom must appear on the left and right sides of the chemical equation. Otherwise, atoms would be gained or lost (i.e. created or destroyed, and not simply transferred). 3. Balancing is done by placing in front of the formulas to ensure the same number of atoms of each element on both sides of the arrow. For now, the will always be whole numbers. 4. Treat chemistry coefficients just like coefficients in algebra. Treat the = sign in algebra. as an 5. Balance either the most obscure elements first or the ones that appear only once on each side of the equation. Always balance the elements and last. 6. If group. ions appear on both sides of an equation, keep them as a 7. If you get stuck, type of atom. all coefficients and start over with a 8. If you still get stuck, try coefficients already entered. 9. Once balanced, you must do three things: 1. 2. 3. or all the