1 Chapter 8 Acids and Bases 8.6 Reactions of Acids and Bases Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Acids and Metals Acids react with metals such as K, Na, Ca, Mg, Al, Zn, Fe, and Sn. to produce hydrogen gas and the salt of the metal. Molecular equations: 2K(s) + 2HCl(aq) 2KCl(aq) + H 2 (g) Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g)

3 Acids and Carbonates Acids react with carbonates and hydrogen carbonates. to produce carbon dioxide gas, a salt, and water. 2HCl(aq) + CaCO 3 (s) CO 2 (g) + CaCl 2 (aq) + H 2 O(l) HCl(aq) + NaHCO 3 (s) CO 2 (g) + NaCl (aq) + H 2 O(l)

4 Learning Check Write the products of the following reactions of acids. A. Zn(s) + 2 HCl(aq) B. MgCO 3 (s) + 2HCl(aq)

5 Solution Write the products of the following reactions of acids. A. Zn(s) + 2 HCl(aq) ZnCl 2 (aq) + H 2 (g) B. MgCO 3 (s) + 2 HCl(aq) MgCl 2 (aq) + CO 2 (g) + H 2 O(l)

6 In a neutralization reaction an acid such as HCl reacts with a base such as NaOH. HCl + H 2 OH 3 O + + Cl − NaOHNa + + OH − the H 3 O + from the acid and the OH − from the base form water. H 3 O + + OH − 2 H 2 O Neutralization Reactions

7 In the equation for neutralization, an acid and a base produce a salt and water. acid base salt water HCl + NaOH NaCl + H 2 O 2HCl + Ca(OH) 2 CaCl 2 + 2H 2 O Neutralization Equations

8 Balancing Neutralization Reactions

9 Write the balanced equation for the neutralization of magnesium hydroxide and nitric acid. STEP 1 Write the acid and base. Mg(OH) 2 + HNO 3 STEP 2 Balance H + in acid with OH - in base. Mg(OH) 2 + 2HNO 3 STEP 3 Balance with H 2 O. Mg(OH) 2 + 2HNO 3 salt + 2H 2 O STEP 4 Write the salt from remaining ions. Mg(OH) 2 + 2HNO 3 Mg(NO 3 ) 2 + 2H 2 O Balancing Neutralization Reactions

10 Select the correct group of coefficients for each of the following neutralization equations A. HCl (aq) + Al(OH) 3 (aq) AlCl 3 (aq) + H 2 O(l) 1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1 3 B. Ba(OH) 2 (aq) + H 3 PO 4 (aq) Ba 3 (PO 4 ) 2 (s) + H 2 O(l) 1) 3, 2, 2, 2 2) 3, 2, 1, 6 3) 2, 3, 1, 6 Learning Check

11 A. 3) 3, 1, 1 3 3HCl(aq + Al(OH) 3 (aq) AlCl 3 (aq) + 3H 2 O(l) B. 2) 3, 2, 1, 6 3Ba(OH) 2 (aq) + 2H 3 PO 4 (aq) Ba 3 (PO 4 ) 2 (s)+ 6H 2 O(l) Solution

12 Basic Compounds in Some Antacids Antacids are used to neutralize stomach acid (HCl).

13 Learning Check Write the neutralization reactions for stomach acid HCl and Mylanta.

14 Solution Write the neutralization reactions for stomach acid HCl and Mylanta. Mylanta: Al(OH) 3 and Mg(OH) 2 3HCl(aq) + Al(OH) 3 (aq) AlCl 3 (aq) + 3H 2 O(l) 2HCl(aq) + Mg(OH) 2 (aq) MgCl 2 (aq) + 2H 2 O(l)

15 Acid-Base Titration Titration is a laboratory procedure used to determine the molarity of an acid. uses a base such as NaOH to neutralize a measured volume of an acid. Base (NaOH) Acid solution Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

16 Indicator An indicator is added to the acid in the flask. causes the solution to change color when the acid is neutralized. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

17 End Point of Titration At the end point, the indicator gives the solution a permanent pink color. the volume of the base used to reach the end point is measured. the molarity of the acid is calculated using the neutralization equation for the reaction. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

18 Calculating Molarity What is the molarity of an HCl solution if 18.5 mL of a M NaOH are required to neutralize 10.0 mL HCl? HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) STEP 1 Given: 18.5 mL of M NaOH; 10.0 mL HCl Need: Molarity of HCl STEP mL L moles NaOH moles HCl M HCl L HCl STEP 3 1 L = 1000 mL mole NaOH/1 L NaOH 1 mole HCl/1 mole NaOH

19 Calculating Molarity (continued) STEP 4 Calculate the molarity of HCl mL NaOH x 1 L NaOH x mole NaOH 1000 mL NaOH 1 L NaOH L moles NaOH x 1 mole HCl = mole HCl 1 mole NaOH M HCl = mole HCl = M HCl L HCl

20 Calculate the mL of 2.00 M H 2 SO 4 required to neutralize 50.0 mL of 1.00 M KOH. H 2 SO 4 (aq) + 2KOH(aq) K 2 SO 4 (aq) + 2H 2 O(l) 1) 12.5 mL 2) 50.0 mL 3) 200. mL Learning Check

21 Solution 1)12.5 mL L KOH x 1.00 mole KOH x 1 mole H 2 SO 4 x 1 L KOH 2 mole KOH 1 L H 2 SO 4 x 1000 mL = 12.5 mL 2.00 mole H 2 SO 4 1 L H 2 SO 4

22 A 25.0 mL sample of phosphoric acid is neutralized by 42.6 mL of 1.45 M NaOH. What is the molarity of the phosphoric acid solution? 3NaOH(aq) + H 3 PO 4 (aq) Na 3 PO 4 (aq) + 3H 2 O(l) 1) M 2) M 3) M Learning Check

23 Solution 2) M L x 1.45 mole NaOH x 1 mole H 3 PO 4 1 L 3 mole NaOH = mole H 3 PO mole H 3 PO 4 = mole/L = M L