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Bell Work
• What is the chemical formula for Barium Hydroxide?
• What is the formula for Calcium Nitrate?
Physical Science – Lecture 44
Writing Chemical Equations
Parts of a Chemical Reaction
• Coefficients – Go in front of the chemical formula. They indicate how many of each chemical is used in the reaction.
Parts of a Chemical Reaction
• Reactants – The chemicals that are reacting in the chemical reaction. They “react” during the reaction. They are written on the left of the arrow.
Parts of a Chemical Reaction
• The Arrow – an arrow separates the reactants from the products in a chemical equation.
Parts of a Chemical Reaction
• Products – The chemicals that are produced by the chemical reaction. They “are formed” from the reaction. They are written on the right of the arrow.
Parts of a Chemical Reaction
• The plus sign – the plus sign separates a reactant from another reactant or a product from another produce in a chemical reaction.
Parts of a Chemical Equation
Translating Word Equations
• Word equations must be translated to chemical equations to determine exactly what is happening in a given reaction.
Elements in an Equation
• All elements when alone are written without charges or subscripts.
• The only exceptions are the diatomic gases – they all have a small subscript 2 behind them.
• N2, O2, F2, Cl2, I2, Br2, and H2
How to Write a Chemical Equation
• Step 1: Translate each compound name to its chemical formula. (Balance the charges of the cation/anion. OR Add subscripts to replace pre-fixes of mono, di, tri, tetra.)
• Step 2: Translate words describing the reaction into symbols.
Words Describing the ReactionWord Symbol
Reacts with +And +
To yield or yield →To form →
Things Reacting Go on the Left of the arrow (→)
Things being Formed Go on the Right of the arrow (→)
Example
• When calcium hydroxide reacts with hydrochloric acid (HCl), calcium chloride and water are formed.
Step 1: Write the unbalanced equation by translating the written names into chemical formulas
• In this case, the formulas you need to know are those for calcium hydroxide, hydrochloric acid, calcium chloride, and water.
• What are the formulas for these compounds?
Step 2: Translate the words into symbols
• When Ca(OH)2 reacts with HCl, CaCl2 and H2O are formed
• When you translate these into their formulas, you should get this equation:
• Ca(OH)2 + HCl --> CaCl2 + H2O
Example 2
• When Tin (II) Oxide reacts with a stream of Hydrogen gas, Tin Metal and water is formed.
Practice
• When potassium nitrate reacts with hydrogen carbonate, nitric acid (HNO3) and potassium carbonate are formed.
Practice
• Methane (CH4) reacts with Oxygen gas to form carbon dioxide and water.
Practice
• Iron and carbon dioxide are formed from the reaction between Iron (III) Oxide and carbon monoxide.
• Carbon dioxide reacts with lithium sulfide to produce carbon disulfide and lithium oxide.
• Magnesium fluoride reacts with lithium carbonate to form magnesium carbonate and lithium fluoride.
• Sodium fluoride reacts with bromine to form sodium bromide and fluorine.
• Aluminum bromide reacts with potassium sulfate to form potassium bromide and aluminum sulfate.
• Sodium phosphate reacts with calcium chloride to form sodium chloride and calcium phosphate.