Single Replacement Net Ionic

1. Single Replacement Net Ionic • 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?

2. 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?

3. 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.

4. Net Ionic for Neutralization • 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.

5. H2SO4 (aq) + 2KOH (aq)  2HOH (l) + K2SO4 (aq) 2H+(aq) + SO42-(aq) + 2K+(aq) + 2 OH-(aq)  2H2O (l) + 2 K+(aq) + SO42-(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) + SO42-(aq) • Yes, the sulfate ions and the potassium ions are both spectators.

6. This leaves us with • 2H+(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

7. Metal reacting with water • If you have a metal reacting with water, how do we predict the products? • Ca + H2O  ??

8. Metal reacting with water (cont.) • 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

9. What factors affect the rate of a chemical reaction?

10. Temperature • 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.

11. 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?

12. Concentration • 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.

13. Surface Area • 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.

14. Catalysts • 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?

15. 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.

16. Pressure of a Gas • 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.

17. What causes the surroundings of a reaction to become either hot or cold following a reaction?

18. Endothermic 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?

19. Exothermic 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?

20. Synthesizing the Standards Lab

21. Before we can go to 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.

22. Preparation for lab (continued) • 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.