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1 Name%% %Period%% % Precipitation+Reaction+Practice+ 1.%Write%a%balanced%equation%for%the%following%precipitation%reactions,%circle%the%precipitate%that%is% formed:% a) K 3 PO 4 %+%3%Sr(NO 3 ) 2 %% % % b) Na 2 S%(aq)%+%ZnCl 2 %(aq)% % % c) Mg(NO 3 ) 2 %(aq)%+%2naoh%(aq)% % % d) Cr 2 (SO 4 ) 3 %(aq)%+%(nh 4 ) 2 CO 3 %(aq)% % % e) Ba(NO 3 ) 2 %(aq)%+%k 2 SO 4 %(aq)% % Looking%at%the%above%reactions,%what%distinguishes%precipitation%reactions%from%acidObase,%and% oxidationoreduction%reaction.% 2.%Which%of%the%following%processes%will%likely%result%in%a%precipitation%reaction?%% a) Mixing%a%NaNO 3% solution%with%a%cuso 4 %solution% b) Mixing%a%BaCl 2 %solution%with%a%k 2 SO 4 %solution% What%distinguishes%these%two%reactions%from%one%another?% % 3.%Will%precipitation%occur%when%the%following%solutions%are%mixed?%% a) Na 2 CO 3 %(aq)%and%agno 3 %(aq)%% % b) NaNO 3% (aq)%and%niso 4 %(aq)% % c) FeSO 4 %(aq)%and%pb(no3) 2 %(aq)% % d) Na 2 CO 3 %(aq)%and%mgso 4 %(aq)% % e) Pb(NO 3 ) 2 %(aq)%and%na 2 S%(aq)% % f) (NH 4 ) 3 PO 4 %(aq)%and%cacl 2 %(aq)%

2 Acids and Bases Mullis adapted by Nieman 1

3 Acids, Bases and Salts Acids give up hydrogen ions (H + ) in a water solution. Bases give up hydroxide ions (OH - ) in a water solution. Mullis 2

4 Naming Acids Binary Acid = 2 elements (HCl) Begin with hydro-. Use name of 2 nd element and end with ic. HCl is hydrochloric acid. Oxyacid = H + O + 3 rd element (H 2 SO 4 ) Usually incorporates the polyatomic ion name into the acid name. Written with H first, then the polyatomic ion. H 2 SO 4 is sulfuric acid. Mullis 3

5 Naming Bases Use regular naming rules. Cation + anion Anion is usually OH- (hydroxide ion) Mullis 4

6 Acid-Base Systems Type Acid Base Examples Arrhenius H + or H 3 O + producer OH - producer HNO 3 + H 2 O H 3 O + + NO 3 - NH 3 + H 2 O NH OH - Brønsted- Lowry Lewis proton (H + ) donor electron pair acceptor proton (H + ) acceptor electron pair donor HCl + NH 3 NH Cl - BF 3 + F - BF 4 - BF 3 is Lewis acid, F - is Lewis base Mullis 5

7 Brønsted-Lowry Acids Brønsted-Lowry acids donate a proton. A monoprotic acid donates one proton per molecule, such as HCl and HClO 4. A polyprotic acid donates more than one proton per molecule, such as H 2 SO 4 and H 3 PO 4. H 2 SO 4 is a diprotic acid. H 3 PO 4 is a triprotic acid. Mullis 6

8 Conjugate acids and bases The species remaining after a Brønsted-Lowry acid gives up its proton is the conjugate base of that acid: Take off one H from the acid. The species remaining after a Brønsted-Lowry base accepts its proton is the conjugate acid of that base: Take off one H. Add an H to the base. CH 3 COOH(aq) + H 2 O(l) H 3 O + (aq) + CH 3 COO - (aq) acid base conjugate conjugate (proton donor) acid base Mullis 7

9 Examples of conjugate acids and bases HCO 3- (aq) + H 2 O(l) H 2 CO 3 (aq) + OH - (aq) base acid conjugate conjugate (proton acid base acceptor) HF(aq) + H 2 O(l) H 3 O + (aq) + F - (aq) acid base conjugate conjugate (proton acid base donor) Mullis 8

10 The Hydronium Ion Ionization is the creation of ions from a molecular compound. If the force of attraction between solvent molecules and parts of the solute are stronger than the covalent bonds of the solute, the solute breaks into ions. In water, HYDRATION produces heat, which provides energy to break more covalent bonds. H + attracts other molecules or ions In water, H + becomes a proton bonded to the oxygen of a water molecule. The hydronium ion is H 3 O +. H Cl H + H H + O H O H + Cl - Mullis 9

11 Salts An acid and base combined together react to neutralize each other. Neutralization is a process which produces products that are not acids or bases. H+ and OH- make water. The remaining reactants combine to make a salt. A salt is an ionic compound made of a metal and a nonmetal. Soap and detergent are organic salts. Mullis 10

12 Neutralization HCl + NaOH NaCl + H 2 O acid base salt water HNO 3 + KOH KNO 3 + H 2 O H + (NO 3 ) - + K + OH - KNO 3 + H 2 O ACID + BASE YIELDS SALT + WATER Mullis 11

13 Neutralization The reaction between an acid and a base which produces a salt and water. Recall: A salt is an ionic compound: metal + nonmetal which is likely to dissociate in water. Ex: You take a dose of the antacid magnesium hydroxide, Mg(OH) 2, to relieve excess stomach acid, HCl. What is the chemical equation for this neutralization reaction? HCl + Mg(OH) 2 MgCl 2 + H 2 O These products are magnesium chloride and water. Mullis 12

14 Acid Strength Strong acids ionize completely in water. Many H 3 O + ions Strong electrolyte Weak acids do not ionize completely in water. Some H 3 O + ions Weak electrolyte The ionized H 3 O + ions are being bonded back to the negative species (reverse reaction) at the same time some acid molecules are being ionized to form H 3 O + ions. Strong and weak bases are similar, except ion involved is OH - instead of H 3 O +. Mullis 13

15 Conjugate Acid Base Pairs Chem Worksheet 19-2 Name An acid is defined as a proton (H + ) donor while a base is a proton acceptor. The substance that is produced after an acid has donated its proton is called the conjugate base while the substance formed when a base accepts a proton is called the conjugate acid. The conjugate acid can donate a proton to the conjugate base, to reform the original reactants in the reverse reaction. Example HF + H 2 O H 3 O + + F acid base c. acid c. base In the reaction above HF is the acid and H 2 O is the base. The HF has given a proton to the H 2 O, forming H 3 O + and F. Since the product H 3 O + can donate a proton back to F it is labeled the conjugate acid, while the F is the conjugate base. Write an equation that shows NH 3 reacting with HCl. Label the acid, base, and conjugate acid and conjugate base. - Write reactants and transfer a proton from the acid to the base: NH 3 + HCl NH Cl H + Acids donate protons Bases accept protons A proton is a hydrogen ion base acid c. acid c. base Rewrite each equation. Identify the acid, the base, the conjugate acid, and the conjugate base in each of the equations. 1. HCl + NH 3 NH Cl 2. OH + HCN H 2 O + CN 3. PO HNO 3 NO 3 + HPO HCO 3 + HCl H 2 CO 3 + Cl Fill in the following table. 5. HCO 3 + OH H 2 O + CO NH H 2 O NH 3 + H 3 O + 7. C 2 O HC 2 H 3 O 2 HC 2 O 4 + C 2 H 3 O 2 8. HPO H 2 O OH + H 2 PO 4 Acid Base Conjugate Acid Conjugate Base Equation 9 HNO 2 H 2 O HNO 2 + H 2 O NO 2 + H 3 O + 10 H 2 O F HF OH 11 NH 3 + HCN NH CN 12 H 2 O ClO 3 13 HSO 4 PO S 2 + H 2 O OH + HS 15 HCO 2 H OH Write an equation that shows the reaction of ammonia, NH 3 with hydrobromic acid, HBr. Label the acid, the base, the conjugate acid, and the conjugate base. 17. Write an equation that shows the reaction of phosphate ion, PO 4 3, reacting with hydronium ion, H 3 O +. Label the acid, the base, the conjugate acid, and the conjugate base. 18. Write an equation that shows the reaction of hydrogen sulfide, HS with hydroxide ion, OH. Label the acid, the base, the conjugate acid, and the conjugate base. John Erickson, 2005 WS19-2ConjugatePairs

16 Redox Reactions The oxidation number changes for at least two elements in the reaction. The most common redox reactions we encounter are single replacement reactions. Oxidation number for a pure element is 0. Oxidation number for metal in an ionic compound is the same as its charge. Oxidation number for O in a compound is -2. Oxidation number for H in a compound is +1. (except peroxides) (except hydrides) In redox reactions, one species LOSES electrons and another GAINS electrons. OIL RIG (LEO says GER.) Oxidation is Losing Reduction is Gaining (Lose electrons = oxidation) (Gain electrons = reduction) Oxidation and reduction happen together. The electrons for reduction come from oxidation. An example: This is a single replacement reaction: Mg + 2AgNO 3 Mg(NO 3 ) 2 + 2Ag Assign oxidation numbers: (free element) If there are any oxidation numbers that changed, the reaction must be redox. If one species is reduced another must be oxidized. Practice: Write the oxidation numbers as requested. If the reaction is a redox reaction, check the box. 9. Zn + 2HCl ZnCl 2 + H 2 redox? 10. CaCO 3 CaO + CO 2 redox? 11. HBr + NaOH H 2 O + NaBr redox?

17 Oxidation Numbers Practice Write the name of each compound and find the oxidation number of each element in the compound. 1. SiBr 4 Si = Br = 2. N 2 O 4 N = O = 3. S 2 Cl 2 S = Cl = 4. NF 3 N = F = 5. PCl 5 P = Cl = Reaction Practice Write the oxidation numbers as requested. If the reaction is a redox reaction, check the box. 6. Cu + 2AgNO 3 Cu(NO 3 ) 2 + 2Ag redox? 7. Fe + Cl 2 FeCl 2 redox? 8. FeCl 3 + 3AgNO 3 Fe(NO 3 ) 3 + 3AgCl redox?

21 ph is related to the concept of concentration of hydronium ions found in water. Water and all its solutions contain hydronium ions and hydroxide ions. Acidic solutions: More H 3 O + ions. Basic solutions: Fewer H 3 O + ions / more OH - ions. If ph = 2: H 3 O + ion concentration = 0.01 M OH - ion concentration = M If ph = 12: H 3 O + ion concentration = M OH - ion concentration = 0.01 M Mullis 4

22 ph stands for power of hydronium ion. ph = -log [H 3 O + ] ph value is the exponent on the power of 10 with its sign changed. Mullis 5

23 ph = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H + ] = 1 X ph = - log 1 X ph = - (- 10) ph = 10 Example: If [H + ] = 1.8 X 10-5 ph = - log 1.8 X 10-5 ph = - (- 4.74) ph = 4.74

24 Find the ph of these: 1) A 0.15 M solution of Hydrochloric acid 2) A 3.00 X 10-7 M solution of Nitric acid

25 H 2 O can function as both an ACID and a BASE. In pure water there can be AUTOIONIZATION Equilibrium constant for water = K w K w = [H 3 O + ] [OH - ] = 1.00 x at 25 o C

26 Autoionization OH - H 3 O + K w = [H 3 O + ] [OH - ] = 1.00 x at 25 o C In a neutral solution [H 3 O + ] = [OH - ] so K w = [H 3 O + ] 2 = [OH - ] 2 and so [H 3 O + ] = [OH - ] = 1.00 x 10-7 M

27 Since acids and bases are opposites, ph and poh are opposites! poh does not really exist, but it is useful for changing bases to ph. poh looks at the perspective of a base poh = - log [OH - ] Since ph and poh are on opposite ends, ph + poh = 14

28 ph [H + ] [OH - ] poh

29 What is the ph of the M NaOH solution? [OH-] = (or 1.0 X 10-3 M) poh = - log poh = 3 ph = 14 3 = 11 OR K w = [H 3 O + ] [OH - ] [H 3 O + ] = 1.0 x M ph = - log (1.0 x ) = 11.00

30 The OH - ion concentration of a blood sample is 2.5 x 10-7 M. What is the ph of the blood?

31 Name: Per Date Solve the following problems. Show all work. ph Practice Problems 1. Find the ph of a solution with [H 3 O + ] = M. Is the solution acidic or basic? 2. Find the ph of a solution with [H 3 O + ] = M. Is the solution acidic or basic? 3. Find the ph for a solution with [OH ] = M. Is the solution acidic or basic? (HINT: find poh and convert to ph) 4. Find the ph for a solution with [OH ] = M. Is the solution acidic or basic? 5. A 0.05 M solution of NaOH contains 0.05 M OH -. Find the poh of this solution and convert to ph. 6. In a blood sample [OH ] = M. Find the ph of blood Is the blood acidic or basic?

FACTORS AFFECTING SOLUBILITY TEMPERATURE AGITATION SURFACE AREA PRESSURE NaCl STRONG ELECTROLYTES - typically ionic compounds & acids. - DISSOCIATE (split into ions) when dissolved in water.

It needs the help of an ELECTROLYTE like NaCl NONELECTROYLTES - typically covalent compounds - DO NOT dissociate into ions, even when they dissolve. Stay MOLECULES.

- DO NOT cause solutions to conduct electricity weakly (a little bit). when dissolving in a Doesn t make Doesn t make it hold more Affects HOW MUCH liquid : it hold more just helps it go FASTER!

in GASES - colder holds less, Could be called: than in dissolves slower. stirring Larger pieces have more solids. shaking middle hidden from mixing the solvent.

Solutions (like KoolAid) have TWO parts: SOLUTE less of (mix & sugar) SOLVENT more of (water) Concentrated: lots of solute (strong Koolaid) Dilute: not holding much solute (weak Koolaid) Saturated

32 FACTORS AFFECTING SOLUBILITY TEMPERATURE AGITATION SURFACE AREA PRESSURE NaCl STRONG ELECTROLYTES - typically ionic compounds & acids. - DISSOCIATE (split into ions) when dissolved in water. - cause solutions to conduct electricity sugar molecule Pure H 20 can t conduct electricity on its own. It needs the help of an ELECTROLYTE like NaCl NONELECTROYLTES - typically covalent compounds - DO NOT dissociate into ions, even when they dissolve. Stay MOLECULES. - DO NOT cause sol s to conduct electricity. WEAK ELECTROYLTES - PARTIALLY dissociate. Some particles stay together, some split up. - DO NOT cause solutions to conduct electricity weakly (a little bit). when dissolving in a Doesn t make Doesn t make it hold more Affects HOW MUCH liquid : it hold more just helps it go FASTER! and HOW FAST but DOES help Solids: it dissolve Smaller pieces have More - hotter holds more, FASTER! more skin touching. important dissolves faster the solvent. in GASES - colder holds less, Could be called: than in dissolves slower. stirring Larger pieces have more solids. shaking middle hidden from mixing the solvent. Liquids at: blending higher pressure hold EX: Sugar cubes dissolve MORE gas Gases (opposite!) slower than regular sugar. lower pressure hold hotter holds LESS gas LESS. colder holds MORE. Solutions (like KoolAid) have TWO parts: SOLUTE less of (mix & sugar) SOLVENT more of (water) Concentrated: lots of solute (strong Koolaid) Dilute: not holding much solute (weak Koolaid) Saturated holding as much solute as it can Unsaturated could hold more solute Supersatured somehow holding MORE solute than should be able to (Ex really sweet ice tea) EX: Soda goes flat flat faster after the cap is opened. Molarity common unit for concentration Molarity (M) = moles of solute (mol) Liters of solution (L) What is the Molarity of a solution containing 3 moles of solute dissolved in a 6 L solution? M = 3 mol = 0.5 M (read as 0.5 Molar) 6 L Properties of ACIDS - Often start with H (EX: HCl, H 2 SO4) - Taste sour - React w/certain metals to produce H 2 (g) - Turn litmus paper RED - Neutralize BASES - React with bases to form Salt & H Produce (H+) Ions (Arrhenius Definition) - proton (H+) DONORS (Bronsted-Lowry) - make solutions with a ph lower than 7 Properties of BASES - Often end with OH (EX: NaOH) - Taste bitter - React with oils and grease (make soap!) - Turn litmus paper BLUE - Neutralize ACIDS - React with acids to form Salt & H proton (H+) ACCEPTORS (Bronsted- Lowry) - Produce (OH-) ions (Arrhenius Definition) - make solutions with a ph higher than 7 Neutralization Reactions: StrongACID + StrongBASE SALT + WATER EX: HCl + NaOH NaCl + H2O Strong Acids (dissociate completely in H2O) HCl, HBr, HI, HNO 3, HClO 3, H 2SO 4, HClO 4 Strong Bases (dissociate completely in H2O) LiOH, NaOH, KOH, RbOH, CsOH Ca(OH) 2, Sr(OH) 2, Ba(OH) 2 If it isn t on the list, assume it is WEAK. Precipitation Reactions Two solutions are mixed and an insoluble substance, known as the precipitate is formed. AgNO 3 (aq) + KCl (aq) AgCl (s) + KNO 3 (aq) (aq) = aqueous-dissolved in solution (s) = solid Oxidation-Reduction Reactions Reaction in which electrons are transferred. - Also known as Redox Reactions See Rules for Oxidation States to see if it is a redox reaction. Ex: 2 Na (s) + Cl 2 (g) 2NaCl (aq) OIL RIG or-- LEO says GER monoprotic acid can give 1 H away (HCl) diprotic acid can give 2 H s away (H 2 SO 4 ) triprotic acid can give 3 H s away (H 3 PO 4 ) amphoteric can be an ACID or a BASE. (Water is an example.) The ph Scale: is a measure of how acidic or basic something is. It is LOGARITHMIC. Each place is 10 times stronger than the next: 2 is 10 times stronger than 3 2 is 100 times stronger than 4 ph means power of Hydrogen, and is roughly a measure of how many H + (or H 3 O + ) are floating around. lower ph => more H + and less OHhigher ph => more OH- and less H + neutral ph => the same H + and OH- ph = -log 10 [H 3 O + ] Example: If an acid has an H + concentration of M, find the ph. Solution: First convert the number to exponential notation, find the log, then solve the ph equation. H + = M = 10-4 log of 10-4 = -4; ph = - log [ H + ] = - log (10-4 ) - (-4) = +4 = ph The purpose of the negative sign in the log definition is to give a positive ph value.

Chapter 14. Objectives

Chapter 14. Objectives Section 1 Properties of Acids and Bases Objectives List five general properties of aqueous acids and bases. Name common binary acids and oxyacids, given their chemical formulas. List five acids commonly