Chemical Equations and Reactions

Describing Chemical Reactions

Describing Chemical Reactions

What are some signs that a chemical reaction is occurring?

Indications of a Chemical Reaction• In a chemical reaction, one or more substances

are changed into one or more NEW substances.

• Indications of a chemical reaction include signs that a new substance has formed.

Indications of a Chemical Reaction1. Evolution of heat and/or light

Indications of a Chemical Reaction2. Production of a gas

Vinegar + baking soda

Indications of a Chemical Reaction3. Formation of a precipitate

(NH4)2S(aq) + Cd(NO3)2 (aq)

Indications of a Chemical Reaction4. Color Change

Phenolphthalein + NaOH

Writing Chemical Equations

Solid sodium oxide is added to water at room temperature and forms sodium hydroxide (dissolved in water).

Write the word equation:Sodium oxide + water sodium hydroxide

Write the formula equation:Na2O(s) + H2O(l) 2 NaOH(aq)

Write formula equations for each of the following chemical reactions.

1. Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water.

2. Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper (II) nitrate.

3. Solid zinc metal reacts with aqueous copper (II) sulfate to produce copper metal and aqueous zinc sulfate.

Translating Chemical EquationsPbCl2 (aq) + Na2CrO4 (aq) PbCrO4 (aq) + 2 NaCl(aq)

Write a sentence explaining the above reaction:

Aqueous solutions of lead (II) chloride and sodium chromate react to form a precipitate of lead(II) chromate and aqueous sodium chloride.

Translate the following into sentences:

1. 2 ZnO(s) + C(s) 2 Zn(s) + CO2 (g)

2. Na2O(s) + 2 CO2 (g) + H2O(g) 2 NaHCO3 (s)

Write and balance equations for each of the following reactions:

1. Calcium metal reacts with water to form aqueous calcium hydroxide and hydrogen gas.

2. Nitrogen dioxide gas reacts with water to form nitric acid and nitrogen monoxide gas.

3. Potassium chlorate decomposes to form potassium chloride and oxygen.

Synthesis1. Iron corrodes in the presence of oxygen forming iron

(III) oxide.

2. Ammonia is formed by the combination of nitrogen and hydrogen at high temperatures and pressure.

Decomposition1. The electrolysis of water results in the formation of

hydrogen and oxygen.

2. When heated, sodium bicarbonate decomposes to sodium carbonate, water, and carbon dioxide.

Single Replacement1. The addition of hydrochloric acid to magnesium

results in the formation of hydrogen gas and magnesium chloride.

2. Sodium reacts violently with water, resulting in the formation of sodium hydroxide and hydrogen gas.

Double Replacement1. When aqueous solutions of potassium iodide and

lead (II) nitrate are mixed, a solid precipitate forms: lead (II) iodide.

2. Hydrochloric acid is neutralized by addition of a base (sodium hydroxide) resulting in the formation of water and a salt.

Combustion1. Ethanol (C2H5OH) burns in oxygen, producing

carbon dioxide and water.

2. Welders use acetylene (C2H2) torches. The flame is produced as acetylene burns in the presence of oxygen.

Using the Activity SeriesZn(s) + H2O(l) no reaction

Sn + O2 SnO2

Cd + Pb(NO3)2 Cd(NO3)2 + Pb

Cu + HCl no reaction

Will the following reactions occur?MgCl2 (aq) + Zn(s)

Al(s) + H2O(g)

Cd(s) + O2 (g)

I2 (s) + KF