Al (s) + SnCl2 (aq)

We would predict that Al would replace Sn.

2Al (s) + 3SnCl2 (aq) 2AlCl3 (aq) + 3Sn (s)

is the complete balanced molecular equation

Why did I predict AlCl3?

Single Replacement Net Ionic

2Al (s) + 3SnCl2 (aq) 2AlCl3 (aq) + 3Sn (s)

Let’s split into complete ionic equation. Every substance that is aqueous will break apart (dissolve) in solution.

2Al (s) + 3 Sn+2(aq) + 6 Cl-(aq) 2Al+3(aq) + 6 Cl- (aq) +3 Sn (s)

Is there anything that looks exactly the same on the left as it does on the right?

2Al (s) + 3 Sn+2(aq) + 6 Cl-(aq) 2Al+3(aq) + 6 Cl- (aq) +3 Sn (s)

Yes, we see that there are 6 Cl- ions on both sides; therefore Cl- is a spectator ion.

This leaves us with our net ionic equation

2Al (s) + 3 Sn+2(aq) 2Al+3(aq) + 3 Sn (s)

Notice that when dissolved (aqueous), substances exist as ions. When solid metal, they don’t exist as ions.

H2SO4 (aq) + KOH (aq)

Since this is a special kind of double replacement known as neutralization or acid/base, we can easily predict the products.

H2SO4 (aq) + 2KOH (aq) 2HOH (l) + K2SO4 (aq)

This is our complete balanced molecular equation. Let’s split into the complete ionic equation.

Net Ionic for Neutralization

H2SO4 (aq) + 2KOH (aq) 2HOH (l) + K2SO4 (aq)

2H+(aq) + SO42-(aq) + 2K+(aq) + 2 OH-(aq) 2H2O (l) + 2 K+(aq) + SO4

2-(aq)

As we look at this, do we find any spectator ions (those present in solution but not active in the reaction)?

2H+(aq) + SO42-(aq) + 2K+(aq) + 2 OH-(aq) 2H2O (l) + 2 K+(aq) + SO4

2-(aq)

Yes, the sulfate ions and the potassium ions are both spectators.

This leaves us with2H+(aq) + 2 OH-(aq) 2H2O (l) as the net ionic equation…..or does it? Is there a way we might simplify?

H+(aq) + OH-(aq) H2O (l)net ionic equation

If you have a metal reacting with water, how do we predict the products?

Ca + H2O ??

Metal reacting with water

Ca + HOH

We see when it’s written this way that it’s a single replacement reaction and we want to see if Ca will replace H.

It does and…

Ca + 2 HOH H2 + Ca(OH)2

Metal reacting with water (cont.)

What factors affect the rate of a chemical

reaction?

An increase in temperature causes the particles to move faster.

When the particles move faster, they collide more often.

As more collisions occur, more collisions will be successful resulting in an increase in the speed of the reaction.

Temperature

If we decrease the temperature, the particles have less energy and will move more slowly.

As the particles slow down, collisions decrease and the reaction also slows down.

Why might you want to cool down a reaction?

Temperature

Concentration means how many particles there are in a particular volume.

The more concentrated a solution is, the more particles are found in the sample.

More particles means that more reactants are available to react and therefore do more rapidly than when there are fewer particles available

3 Molar hydrochloric acid reacts faster than 0.5 Molar hydrochloric acid.

Concentration

The more surface area there is, the faster a reaction will progress.

Which has more surface area?◦ copper sheet metal◦ copper strips◦ copper wire◦ copper pellets◦ copper powder

The copper powder has the greatest surface area (most sides available to react) and will therefore react most quickly.

Surface Area

Adding a catalyst lowers the energy needed for a reaction to occur which thereby speeds up the reaction.

A catalyst in chemistry has the same role as an enzyme in biology.

An inhibitor is a “negative” catalyst and will slow a reaction.

Are there inhibitors in anything you consume?

Catalysts

   

is the way that you show a catalyst is used in a reaction.  The V2O5 does not participate in the reaction; instead, it serves as a catalyst to allow the reaction to occur more quickly.

Catalysts

If you have gaseous reactants, pressure can impact the speed of the reaction.

Increased pressure means that the gaseous particles are closer together.

If they’re closer to one another, they bump into each other more often.

Increased pressure then means that gaseous reactants will react faster.

Pressure does not impact solid or liquid reactants appreciably.

Pressure of a Gas

What causes the surroundings of a

reaction to become either hot or cold

following a reaction?

When energy is required to make a process occur, the energy is absorbed from the immediate surroundings.

This makes the temperature of the surroundings decrease.

We observe that the surroundings become cold.

Have you seen this in lab? When?

Endothermic Reaction

When a reaction gives off energy, it usually gives it off in the form of heat.

This makes the immediate surroundings warm up as the heat flows into them.

Have you witnessed this in lab? When?

Exothermic Reaction

Synthesizing the Standards Lab

We must do several things in preparation for the actual lab.

Look at your lab handout. Write the skeletal equation for the first

reaction. Be sure that your formulas are correct. Include states of matter. Balance this equation. Identify the type of reaction.

Before we can go to lab….

After you are satisfied with your balanced complete molecular equation, write your balanced complete ionic equation.

Find any spectator ions and cross them out. Write your correctly balanced net ionic

equation. Now, you’re ready to carry out the

experiment! Be sure to make note of ALL observations. Write the appropriate INDICATORS that a

reaction occurred.

Preparation for lab (continued)