Lab 4 Chemical reactions

A.Signs of a Chemical Reaction Evolution of heat and light Formation of a gas Formation of a precipitate Color change

B.Law of Conservation of Mass mass is neither created nor destroyed in a chemical reaction 4 H 2 O 4 H 2 O 4 g32 g 36 g total mass stays the same atoms can only rearrange

Predicting products Example: 2KClO 3 2KCl + O 2 Products are predicted based on lab analysis using physical properties The product produces is a clear flammable gas, has to be O 2

Part A1 (1-4) Rxn between Cu and Sulfur pg 38 Will be demonstrated –Answer questions 1-4 on page 43 as they relate to page 38

Part A2 (5-7) continued Rxn between Cu and Sulfur pg 38 Copper (II) Sulfide, CuS is insoluble in NH 3(aq) Copper (I) Sulfide, Cu 2 S is soluble in NH 3(aq) and produces a blue soln

Oxidation – Involves the loss of electrons. The species that undergoes oxidation is the reducing agent. Reduction – Involves the gain of electrons. The species that undergoes reduction is the oxidizing agent. Note: If one substance is oxidized then another substance is reduced. Part B oxidation - reduction

Oxidation Ex # 1 Na 0 (s) →Na 1+ +1e - Na looses 1 electron Ex # 2 Zn 0 → Zn 2+ +2e - Zn looses 2 electrons Remember – Ox is the loss of electrons; the one that looses electrons is also called the reducing agent.

Reduction Is the gain of electrons; the one that gains electrons is the oxidizing agent Cl 1+ +1e - → Cl Ex #3 Cl gains 1 electron Ex #4 N +5 +1e - → N 4 Nitrogen gains 1electron It is called reduction because you are reducing the charge

Fe + CuSO 4 (aq)  Cu + FeSO 4 (aq) Fe 0 (s)  Fe +2 (aq) + 2e - (oxidation) Cu +2 (aq) + 2e -  Cu 0 (s) (reduction) Iron looses two electrons, and Copper gains two. Single replacement

Part B (8,9) Add a small piece of Zn to a test tube containing 2ml 6M HCl (dangerous) Record observations Answer questions 8,9 on page 39 Zn + HCl (aq) 

Part B (10,11) Repeat procedures with a 1 inch copper wire Record observations Answer questions 10,11, on page 39 Cu + HCl (aq) 

Part B3 (12-15) Must be done in hood!!! Place a 1 inch copper wire in a test tube with 1ml of conc. HNO 3 (Dangerous) Look at the gas produced and predict rxn based off of table 4.1 on page 39 Cu + HNO 3 (aq) 

Part B (12-15) Answer questions 12-14, After rxn proceeded for five minutes add 5 ml of H 2 O Answer questions 15 based on table 4.1, on page 39

2Mn (+7)  Mn +2 turns pink and is reduced Part B (16) 2MnO H 2 C 2 O H +  M n CO 2 (g) + 8H 2 O (aq)

Part B (16) Place 1ml of 0.1 M Sodium Oxalate Na 2 C 2 O 4 in a clean test tube. Add 10 drops of 6 M H 2 SO 4 (Dangerous) Add 2 drops of 0.1M KMnO 4 Record observations Answer questions 16, based on table 4.1 on page 39

Part B (17 ) Place 3ml of 0.1 M NaHSO 3 in a clean test tube. Add 1ml of a 10 M NaOH (Dangerous) Add 2 drops of 0.1M KMnO 4 Record observations

Part B (18, 19 ) Add an additional 0.1M KMnO 4, one drop at a time, until 10 drops have been added. Record observations Answer questions 18,19 on page 40

Part B Omit KMnO 4 with HCL, use data given by teacher –20. KMnO 4 dissolves –21. Pungent odor and a pale yellow green gas is produced

Part C Metathesis AB + CD (aq)  AD + CB NaCl + AgNO 3 (aq)  NaNO 3 + AgCl

Part C (23-26) Place a small sample of Na 2 CO 3 in a test tube and add several drops of 6M HCl (Dangerous) Look at the product produced and predict rxn based off of table 4.1 on page 39 Na 2 CO 3 + HCl (aq) 

Note H 2 CO 3  H 2 O + CO 2 H 2 SO 3  H 2 O + SO 2

Part C (27-29) Place a small sample of Na 2 SO 3 in a test tube and add several drops of 6M HCl (Dangerous) Look at the product produced and predict rxn based off of table 4.1 on page 39 Na 2 SO 3 + HCl (aq) 

Part C (30-32) Must be done in Hood!!! Place a small sample of ZnS in a test tube and add several drops of 6M HCl (Dangerous) Look at the product produced and predict rxn based off of table 4.1 on page 39

Part C (33-38) Omit PbNo 3 with HCL, use data given by teacher –33. A white precipitate forms –34 PbCl 2. Omit BaCl 2 with K 2 CrO 4, use data given by teacher –36. A yellow precipitate forms –37 BaCrO 4 Look at table 4.1 on page 39 and predict rxn

Part C5 (39-43) Omit BaCl 2 with (NH 4 ) 2 CO 3, use data given by teacher –39. BaCO 3 –41, 43. A gas formed that was colorless and odorless –Answer questions 39-43, based on table 4.1 on page41

Due next week Pgs Study for next weeks quiz 5