.Very little change until endpoint 3.Sharp rise in pH at endpoint (neutral salt) 4.High pH after endpoint (Excess **Base**) Strong **Acid**/Strong **Base** **Titration** A stoichiometry **problem** (reaction is assumed to run to completion) then determine concentration of **acid** or **base** remaining. The salt formed is neutral. HCl + NaOH H 2 O + NaCl I C E Work in Moles! Then calculate concentration (Molarity)! You will/

expands it beyond recognition. The Chemistry of **Acids** and **Bases** **Acids** and **Bases**: **Titration** At the conclusion of our time together, you should be able to: 1. Do a **titration** of an **acid** with a **base** 2. Calculate the equivalence point (neutralization point) for a **titration** **problem** 3. Define normality 4. Determine the percent **acid** with a **titration** **problem** You will pay, I guarantee it!!! During a **titration**, the indicator goes in the 1/

. When the indicator changes color permanently, we’ve reached our endpoint (when we stop **titrating**). The endpoint is close to, but not exactly, the equivalence point, which is when the **acid** and **base** have neutralized each other. **Titration** Practice When solving a **titration** **problem**, you need to write the balanced reaction. – Remember, **acids** + **bases** form water and a salt. Step 1: Find the moles (using the molarity) of/

**acid**] = [conj. **base**] or [weak **base**] = [conj. **acid**] [H 3 O + ] = K a and pH = pK a @ equivalence point: mol **acid** = mol **base**; equilibrium **problem** with conjugate @ equivalence point: mol **acid** = mol **base**; equilibrium **problem** with conjugate Beyond equivalence point – pH **based** on excess titrant; stoichiometry Beyond equivalence point – pH **based** on excess titrant; stoichiometry Test #2 Summary for **Acid**/**Base** **problems** 1. Weak **acid** or weak **base** only (ch. 16) 2. Buffer 3. SA + SB **Titration** 4/

unknown concentration is called a **titration**.**Titration** 19.4 Neutralization Reactions > 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The steps in an **acid**-**base** **titration** are as follows: 1.A measured volume of an **acid** solution of unknown concentration is /or its affiliates. All Rights Reserved. Calculate Solve for the unknown. 2 Use the molarity to convert the volume of **base** to moles of **base**. Sample **Problem** 19.8 0.018 L NaOH × 1.0 mol NaOH 1 L NaOH = 0.018 mol NaOH 19.4 /

higher than 7 are used to determine the equivalence point of weak-**acid**/strong-**base** **titrations**. weak-**acid**/strong-**base** = basic **Titration** Curve Strong **Acid** and a Strong **Base** Equivalence Point: pH at 7 **Titration** Curve Weak **Acid** and a Strong **Base** Equivalence Point: pH higher than 7 **Titration** Curve Strong **Acid** and a Weak **Base** Equivalence Point: pH less than 7 **Titration** **Problems**: * Can be used to determine concentration of unknown solution or volume of/

.0ml of Ba(OH) 2. What is the concentration of the barium hydroxide? Tuesday 6/21/05 Prep: 1. Get copies of **Acid**-**Base** Mini-Exam 2. Make fine cards! Class: 1. Pass out AP Bio stuff. 2. Review a **titration** **problem**. 3. **Acid**-**Base** Mini-Exam 4. Pass back finals / fine cards / check basmati/ sign annuals. Plan: 1. Fill out fine cards! 2. Call Mary/

new pH can be calculated by putting the concentration of the anion into the K a equation and solving for the new [H + ]. Understanding common ion **problems** aides understanding of buffer solutions, **acid**-**base** indicators and **acid**-**base** **titration** **problems**. Example **problem** Determine the [H 3 O + ] and [C 2 H 3 O 2 - ] in 0.100 M HC 2 H 3 O 2. The K a for/

.0250 L HCOOH M HCOOH = 7.31x10 -2 M Practice **Acid**-**Base** **Titration** **Problems** 44 – 46 page 664 **Problems** 52, 54 page 668 **Problems** 86 – 89, 92 – 93 page 673 **Problems** 24 – 25 page 989 Salt Hydrolysis Put salt in pure water Unless salt product of strong **acid**/strong **base** reaction, pH won’t be neutral Neutral Basic **Acidic** NaNO 3 KF NH 4 Cl Salt Hydrolysis KF(s) K/

expands it beyond recognition. The Chemistry of **Acids** and **Bases** **Acids** and **Bases**: **Titration** At the conclusion of our time together, you should be able to: 1. Do a **titration** of an **acid** with a **base** 2. Calculate the equivalence point (neutralization point) for a **titration** **problem** 3. Define normality 4. Determine the percent **acid** with a **titration** **problem** You will pay, I guarantee it!!! Lemonade **Titration** **Problem** 0.100 M x 1 x 8/

pH Curves Return to TOC Copyright © Cengage Learning. All rights reserved 91 Weak **Acid**–Strong **Base** **Titration** Step 1:A stoichiometry **problem** (reaction is assumed to run to completion) then determine remaining species. Step 2: An equilibrium **problem** (determine position of weak **acid** equilibrium and calculate pH). Section 15.4 **Titrations** and pH Curves Return to TOC Copyright © Cengage Learning. All rights reserved 92 Concept Check Calculate/

as in the strong **acid**/strong **base** example. 68 Weak **Acid**/Strong **Base** **Titration** Curves We have calculated only a few points on the **titration** curve. Similar calculations for remainder of **titration** show clearly the shape of the **titration** curve. 69 Strong **Acid**/Weak **Base** **Titration** Curves **Titration** curves for Strong **Acid**/Weak **Base** **Titration** Curves look similar to Strong **Base**/Weak **Acid** **Titration** Curves but they are inverted. 70 Weak **Acid**/Weak **Base** **Titration** Curves Weak **Acid**/Weak **Base** **Titration** curves have very/

a strong **acid** (HCl) with a strong **base** (NaOH). Interpret Graphs If the **titration** of HCl and NaOH could be stopped right at the equivalence point, the solution in the beaker would consist of only H 2 O and NaCl, plus a small amount of indicator. 19.4 Neutralization Reactions > 27 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample **Problem** 19/

x Va = Mb x Vb Ma – molarity of **acid** Va – volume of **acid** Mb – molarity of **base** Vb – volume of **base** See Ch 14/15 handout for more info. 40 Sample **Problem** 524/24 Determine the number of moles of the first substance that would be chemically equivalent of the second substance in these **acid**-**base** **titrations**: a.NaOH with 1.0 mol HCl b.HNO 3 with/

more dramatic the pH change x Weak **titrated** with strong In an **acid**/**base** **titration** in which one substance is strong and the other weak… The solution is not neutral at the equivalence point due to the hydrolysis of the salt. So we have to work with a series of buffer **problems**. Working first the stoichiometry **problem**, then the equilibrium **problem**. Calculate pH when 50.0 mL/

as in the strong **acid**/strong **base** example. 68 Weak **Acid**/Strong **Base** **Titration** Curves We have calculated only a few points on the **titration** curve. Similar calculations for remainder of **titration** show clearly the shape of the **titration** curve. 69 Strong **Acid**/Weak **Base** **Titration** Curves **Titration** curves for Strong **Acid**/Weak **Base** **Titration** Curves look similar to Strong **Base**/Weak **Acid** **Titration** Curves but they are inverted. 70 Weak **Acid**/Weak **Base** **Titration** Curves Weak **Acid**/Weak **Base** **Titration** curves have very/

more obvious if there is none vs. some. 44 45 **Acid**/**Base** **Titrations** How does this work for an **acid**/**base** **titration**? What is the first thing we need to know? EXACTLY! The Chemical Reaction 46 **Acid**-**base** Reaction In an **acid**/**base** **titration**, the generic reaction is: H + + OH - /**bases** have an OH: HCl + NH 3 ??? NH 3 + H 2 O = NH 4 OH HCl + NH 4 OH H 2 O + NH 4 Cl You can always generate OH - in water, because water can always act as an **acid**. 75 A little bitty **problem**… A 10.00 mL sample of waste water is **titrated**/

Oxidation-Reduction (Redox) **Titration** An oxidation-reduction **titration** (redox **titration**) is a **titration** **based** on an oxidation-reduction reaction. Calculations are done in the same way as in **acid**-**base** **titrations**. Example: A 20.00 mL sample of a solution containing Fe 2+ ion is **titrated** with a 0.02418 / the concentration of the Fe 2+ solution, using the number of moles (found in step 2) and the volume of Fe 2+ solution (given in the **problem**). 6 Fe 2+ (aq) + BrO 3 - (aq) + 6 H + (aq) 6 Fe 3+ (aq) + Br - (aq)/

1.0 M HCI Copyright © Cengage Learning. All rights reserved 29 Section 15.4 **Titrations** and pH Curves Weak **Acid**–Strong **Base** **Titration** Step 1:A stoichiometry **problem** (reaction is assumed to run to completion) then determine concentration of **acid** remaining and conjugate **base** formed. Step 2: An equilibrium **problem** (determine position of weak **acid** equilibrium and calculate pH). Copyright © Cengage Learning. All rights reserved 30 Section 15.4/

value. Find the pH and the pOH of each solution described in practice **problems** 1a-d on page 477. 14 Practice: find the pH; pOH; /**Titration** Calculations: we use **titrations** to find the concentration of an **acid** or **base** solution. Remember that at the Equivalence point: n **acid** = n **base** M **acid** V **acid** = M **base** V **base** An **acid**-**base** **titration** usually starts with an **acid** solution of unknown concentration. We accurately measure the amount of **acid** solution we want to use in the **titration** (V **acid** ). We start to add a **base**/

HCl with NaOH. –To detect the equivalence point, you need an **acid**-**base** indicator that changes color within the pH range 3-11. –Phenolphthalein can be used because it changes color in the pH range 8.2-10. (see Figure 16.10) **Titration** of a Strong **Acid** by a Strong **Base** 6 A **Problem** To Consider Calculate the pH of a solution in which 10.0/

Solution: 1.balanced neutralization equation chemically equivalent amounts Molarity and **Titration**, continued Sample **Problem** F Solution, continued 2. volume of known basic solution used (mL) amount of **base** used (mol) Chapter 15 Section 2 Determining pH and **Titrations** 3. mole ratio, moles of **base** used moles of **acid** used from unknown solution Molarity and **Titration**, continued Sample **Problem** F Solution, continued 4. volume of unknown, moles of solute/

NaOH to the equivalence point. pH at equivalence point? pH of solution of benzoic **acid**, a weak **acid** Benzoic **acid** + NaOH pH at half-way point? 72 **Acid**-**Base** Reactions Strategy — find the conc. of the conjugate **base** Bz - in the solution AFTER the **titration**, then calculate pH. This is a two-step **problem** 1. stoichiometry of **acid**-**base** reaction 2. equilibrium calculation Strategy — find the conc. of the conjugate/

(1.49 M) **Problem** n How many moles of 0.275 M HCl will be needed to neutralize 25.0 mL of 0.154 M NaOH? HCl + NaOH NaCl + H 2 O (0.0140 moles) **Titration** Curves A plot of pH versus volume of **acid** (or **base**) added is called a **titration** curve. **Titration** Curves Strong **Base**-Strong **Acid** **Titration** Curve **Titration** Curves Consider adding a strong **base** (e.g. NaOH/

Solution: 1.balanced neutralization equation chemically equivalent amounts Molarity and **Titration**, continued Sample **Problem** F Solution, continued 2. volume of known basic solution used (mL) amount of **base** used (mol) Chapter 15 Section 2 Determining pH and **Titrations** 3. mole ratio, moles of **base** used moles of **acid** used from unknown solution Molarity and **Titration**, continued Sample **Problem** F Solution, continued 4. volume of unknown, moles of solute/

**acid** or a **base** through the use of an **acid**-**base** reaction is called an **acid**-**base** **titration**. **Titration** **Titration** n The known reactant molarity is used to find the unknown molarity of the other solution. n Solutions of known molarity that are used in this fashion are called standard solutions. **Titration** n In a **titration**, the molarity of one of the reactants, **acid** or **base**, is known, but the other is unknown. **Problem**/

- ] = 4.0 mmol / 80.0 ml = 0.05 M **TITRATION** CURVES Monoprotic **Acids** pH Vol SB 7 SA - SB **TITRATION** CURVES Monoprotic **Acids** pH Vol SB 9 WA - SB **TITRATION** CURVES Monoprotic **Acids** pH Vol SA 3.5 SA - WB **TITRATION** CURVES Polyprotic **Acids** pH Vol **Base** H 2 SO 4 HSO 4 - pK a1 SO 4 -2 pK a2 **Problem** 25.0-mL of 0.145 M HCl soln/

in **acid**-**base** **problems** are given to us in terms of pH (power of H + ) and pOH (power of OH - ). Many of the concentration measurements in **acid**-**base** **problems** are /**acid**. Reaction rate SLOWS down as 100% neutralization approaches. Need EXCESS **base** to FULLY ionize the weak **acid** for complete neutralization Strong **acid**-Weak **base** **Titration** PREDICT: How will a strong **acid**-weak **base** curve differ from strong **acid**- strong **base** curve? PREDICT: How will a strong **acid**-weak **base** curve differ from strong **acid**- strong **base**/

will look only at the initial step NEUTRALIZATION REACTIONS Double displacement Reaction between **acid** and **base** Salt and water form Salt – is an ionic compound made up of a cation from a **base** and an anion from an **acid**. Write the equation for the reaction of magnesium hydroxide and hydrochloric **acid** **ACID**/**BASE** **TITRATION** Method for determining the concentration of a solution by reacting a known volume of/

on buffered solutions require exactly the same procedures introduced in Chapter 14. This is not a new type of **problem**." “When a strong **acid** or **base** is added to a buffered solution, it is best to deal with the stoichiometry of the resulting reaction first./ pH of the solution as an **acid**-**base** **titration** proceeds from beginning to well beyond the equivalence point pH is plotted on the y-axis and volume of **base** (or **acid**) delivered is plotted on the x-axis Shape of **titration** curve makes it possible to identify /

between pH 4 and 10 Equivalence point between pH 4 and 10 Equivalence point is reached when equivalents of **base** (or **acid**) added equal to equivalents of **base** (or **acid**) initially present Strong **Acid** **Titrated** with Strong **Base** **Titration** **Problems** Can be solved using charge balance. If strong HCl is **titrated** with strong NaOH NaOH + HCl → H 2 O + Na + + Cl - Charge balance [Na + ] + [H + ] = [OH - ] + [Cl - ] to get the/

+ 30 mL = 0.040 L 10mL: Just a buffer….NH 3 and NH 4 + pOH = pK b + log (**acid**/**base**) pH = 14 - 4.32 = 9.67 pOH = 4.74 + log (.00625/0.01625) = 4.74 – 0.41 = 4.32 **Titration** of a weak **base**… Try a **titration** **problem**: **Titrate** 30 mL of 0.030 M NH 3 with 0.025 M HCl. What is the pH after/

moles per liter) V: volume (in liters) of the solution **Titration** Calculations An easier way to think of this: (C **Acid**)(V **Acid**) = (C **Base**) (V **Base**) C: concentration (in moles per liter) V: volume (in liters) of the solution (CAcid) (VAcid) = (CBase) (VBase) Sample **Problem** D, pg. 555 Calculating Concentration from **Titration** Data A student **titrates** 40.00 mL of an HCl solution of unknown concentration with/

added 50.0 mL NaOH 0.00250 mol NaOH xs pH = 12.52 37 Tro: Chemistry: A Molecular Approach, 2/e **Titrating** Weak **Acid** with a Strong **Base** The initial pH is that of the weak **acid** solution – calculate like a weak **acid** equilibrium **problem** e.g., 15.5 and 15.6 Before the equivalence point, the solution becomes a buffer – calculate mol HA init and/

exactly equal the amount of **acid** you started with. Moles of **Acid** = Moles of **Base** The equation for **titration** calculations is At neutralization, Moles of **Acid**= Moles of **Base** M a V a = M b V b Ma = **Acid** Molarity Mb = **Base** Molarity Va = **Acid** volume Vb = **Base** Volume Volumes can be any units as long as they are the same on both sides! Example **Titration** **Problem** If 5.00mL of 1/

.e. H 2 SO 4 ): two equivalence points Calculations involving **Titrations** of Weak **Acids**/**Bases** Divide the **titration** into the following points: 1. Starting point: No **acid**/**base** added (**acid**/**base** in water **problem**) Starting Point Use a two step procedure when calculating pH prior to the equivalence point whenever a strong **acid**/**base** is added to a weak **acid**/**base**. Before Equivalence Point 2. Before the equivalence point (Note: for weak a/

There are many different types of hydrolysis reaction, but in this **problem**, hydrolysis refers to a reaction between water and the anion of the weak **acid**. Hydrolysis means "cleavage by means of water". There are many/**acid**-strong **base** **titration** curve is exactly 7 because the salt produced does not undergo any hydrolysis reactions. **Titrating** Weak **Acids** with Strong **Bases** If a strong **base** is used to **titrate** a weak **acid**, the pH at the equivalence point will not be 7. If a strong **base** is used to **titrate** a weak **acid**/

either the HCl or KOH (as appropriate). 7/13/2015 Please Pick Up Blank IDIRICE grids Small lettered **titration** volume sheet Aqueous Neutralization Reactions Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology **Problem** Set Weak **Acid** – Strong **Base** **Titration** 7/13/2015 Potentiometric **Titration** 20.0 mL of 0.400 M HCl with Aqueous Ammonia 0481216202428 0 2 10 8 6 4 pH/

is determined, and the pH is calculated. Figure 8.3: The pH curve for the **titration** of 50.0 Weak **acid** Calculating the pH During a Weak **Acid**-Strong **Base** **Titration**–I **Problem**: Calculate the pH during the **titration** of 20.00 mL of 0.250 M nitrous **acid** (HNO 2 ; K a = 4.5 x 10 -4 ) after adding different volumes of 0.150 M NaOH : (a/

pH Curves Return to TOC Copyright © Cengage Learning. All rights reserved 23 Weak **Acid**–Strong **Base** **Titration** Step 1:A stoichiometry **problem** (reaction is assumed to run to completion) then determine remaining species. Step 2: An equilibrium **problem** (determine position of weak **acid** equilibrium and calculate pH). Section 15.4 **Titrations** and pH Curves Return to TOC Copyright © Cengage Learning. All rights reserved 24 Concept Check Consider/

27 of 45 General Chemistry: Chapter 17 Prentice-Hall © 2007 **Titration** Curve For Strong **Acid** - Strong **Base** **Acid**-**Base** **Titrations**/Indicators Indicators should change color close to the equivalence point. **Acid**-**Base** **Titrations**/Indicators Phenolphthalein is used in a strong **acid**/strong **base** **titration** the solution turns pink upon the addition of a certain amount of **base**. Upon the addition of more **base** the solution turns colorless. Explain 2012 AP QUESTION 1 (a) Explain/

equation is NOT 1:1 then you must rely on the mole relationship and handle the **problem** like any other stoichiometry **problem**. MOLES OF **ACID** = MOLES OF **BASE** nacid = nbase Ma Va = Mb Vb rearranges to Ma = Mb Vb / Va **TITRATION** MAVA = MBVB 1. Suppose 75.00 mL of hydrochloric **acid** was required to neutralize 22.50 mL of 0.52 M NaOH. What is the/

higher the pH at the EQ point. Indicators must be chosen **based** on the pH of the equivalence point Curve of a diprotic **acid** (eg. H2CO3 or H2SO4): two equivalence points Calculations involving **Titrations** of Weak **Acids**/**Bases** Divide the **titration** into the following points: 1. Starting point: No **acid**/**base** added (**acid**/**base** in water **problem**) Starting Point 2. Before the equivalence point (Note: for weak a/b at the/

= (.015)(1) .0150 N KOH Use the **titration** formula to find the normality of the **acid**: N a V a =N b V b (x)(15.7 mL) = (.0150 N)(17.4 mL) x =.0166 N Convert normality to molarity: M = N / n x =.0166 N / 2 x =.00831 M **Titration** **Problems** Ex 3: In a **titration** of 27.4 mL of 0.0154 M/

react with some of the ammonia and change the concentrations of the species. – This is another limiting reactant **problem**. HCl + NH 3 → NH 4 Cl Initial0.02 mol0.1 mol0.2 mol change-0.02 mol /32 pH=11.68 42 Weak **acid**-strong **base** 44 Strong **Acid**/Weak **Base** **Titration** Curves **Titration** curves for Strong **Acid**/Weak **Base** **Titration** Curves look similar to Strong **Base**/Weak **Acid** **Titration** Curves but they are inverted. 45 Weak **Acid**/Weak **Base** **Titration** Curves Weak **Acid**/Weak **Base** **Titration** curves have very short vertical /

a salt and water An **acid**-**base** **titration** is the determination of the concentration of an **acid** or **base** by exactly neutralizing the **acid**/**base** with an **acid** or **base** of known concentration. This allows for quantitative analysis of the concentration of a unknown **acid** or **base** solution. An **acid**-**base** **titration** in which a **base** is **titrated** with a standard solution of an **acid** is called Acidimetric An **acid**-**base** **titration** in which an **acid** is **titrated** with a standard solution/

Reactions OBJECTIVES: – Define the products of an **acid**-**base** reaction. – Explain how **acid**-**base** **titration** is used to calculate the concentration of an **acid** or a **base**. – Explain the concept of equivalence in neutralization reactions. Agenda Day 74 – **Acid** & **Base** **Titration** - Stoichiometry/pH Calculations Lesson: PPT Handouts: 1. **Titration** Handout 2. **Titration** **Problems** Worksheet Text: 1. P. 476- 484 -**Titration** HW: 1. P. 485 # 1-13 **Acid**-**Base** Reactions **Acid** + **Base** → Water + Salt Properties related to every day/

mol before after Notice the product F - is a conjugate **base**. Some F - will react with water to produce OH - How much? Do the equilibrium **problem** It requires.0050 mol NaOH to neutralize the **acid**; L =.0050 mol / 0.10 M NaOH =.050 L = 50 ml NaOH The **titration** is at the equivalence point. **Titrate** 50.0 mL of 0.10 M HF (Ka = 7/

[H + ] P MEANS NEGATIVE LOG AND THE BRACKETS AROUND H + MEANS “CONCENTRATION OF H + ” SAMPLE **PROBLEM**: WHAT IS THE PH OF A SOLUTION WHEN ITS [H + ] = 0.000001 M ? SOLUTION: 0./**ACID** – **BASE** **TITRATION** (ALSO CALLED EQUIVALENCE POINT), MOLES OF H + IONS ADDED FROM THE **ACID** EQUAL MOLES OF OH - IONS ADDED FROM THE **BASE**. N **ACID** = MOLES H + / LITERS MOLES H + = N **ACID** x LITERS N **BASE** = MOLES OH - / LITERS MOLES OH - = N **BASE** x LITERS AT ENDPOINT MOLES H + = MOLES OH - THEREFORE: N **ACID** x VOL **ACID** = N **BASE** x VOL **BASE**/

in a solution may also affect the indicator’s dissociation. Using indicator strips can help overcome these **problems**. pH Meters A pH meter makes rapid, accurate pH measurements. often easier to use than liquid indicators/**Titration** You can determine the concentration of **acid** or **base** in a solution by performing a neutralization reaction. You must use an appropriate **acid**-**base** indicator to show when neutralization has occurred.appropriate **acid**-**base** indicator In the lab, typically phenolphthalein for **acid** **base**/

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