7.2 Writing Chemical Equations

By: Jake Poserina and Tyler Dunphy

What is a Chemical Equation?

• A Chemical Equation is an expression representing a chemical reaction

• The reactants on the left and the formula of the products on the right

• These reactants are connected by an arrow called a yield

• Ex. Fe + O₂ → Fe₂O₃

Symbols Used In Chemical Equations

Skeleton Equations

• A Skeleton Equation is a chemical equation that does not indicate the relative amounts of the reactants and products. Use (s) for soled, (l) for a liquid, (g) for a gas, (aq) for an aqueous solution.

Catalysts

• A catalyst is a substance that speeds up a reaction without being used up.

• Because a catalyst is neither a reactant nor a product, its formula is written above the arrow in a chemical equation.

MnO₂ H₂O₂→H₂O(l)+O₂(g)

Question 1

Write a skeleton equation for this chemical reaction: when calcium carbonate is heated,

calcium oxide and carbon dioxide are produced.

∆

CaCO₃(s)→CaO(s)+CO₂(g)

Question 2

Solid sulfur burns in oxygen gas to form sulfur dioxide gas.

S+O₂→SO₂

Oxygen gas can be made by heating potassium chlorate in the presense of the catalyst manganese (IV) oxide. Potassium chloride is left as a solid residue.

A. CaCO₃(aq)→CaO+CO₂

B. KClO₃→KCl+MnO₅

C. KClOMn→ClO+KMn

D. KClO₃+MnO₂→KCl+MnO₅

When solid mercury(II) sulfide is heated with oxygen, liquid mercury metal and gaseous sulfur dioxide are produced

A. HgS+O₂→Hg+SO₂

B. HgS→Hg+SO₂

C. HgSO→Hg+SO

Shout out to my favorite teacher @scottsweeten! #scienceproject

Mr. Sweeten’s class unit 7.2

Tyler Dunphy & Jake Poserina

Homework:Write a Vendiagram on the difference's of skeletal equations, and regular chemical equations.