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.