Lab 5 Classification of Chemical Reactions

Transcription

1 Lab 5 Classification of Chemical Reactions Due Date Name Partner Chemistry B1A/Summer 2015 / Daniel 1 Purpose The purpose is to familiarize you with different types of reactions, and to practice writing molecular, ionic, and net ionic reactions. Before mixing reactants, record your observations in your lab notebook. Include reactants physical state such as solid, liquid, or gas, and color, and if it is homogeneous or heterogeneous. After mixing again record your observations. If a liquid becomes cloudy it is because a solid product formed in the liquid making a heterogeneous mixture. Also note color changes and if the mixture becomes hot or cold. When finished dispose of the products. Solids larger than powder will go in a trash can. Reaction 12 with silver cations and metal will need to go in the heavy metal waste container. Classify the type of reaction and circle your answer as either double replacement (DR), decomposition (D), combination (C), combustion (Co), single replacement (SR), or NAR for no apparent reaction. There may be more than one answer. Balance the reactions and fill all blanks, even with a 1. Write the ionic and net ionic equation and show the states of all reactants and products (such as s for solid, g for gas, aq for dissolved in water, and L for liquid). 1. Mix 2 ml of 0.1 M calcium chloride with 2 ml of 0.1 M sodium phosphate in a small test tube. Molecular Equation CaCl 2 (aq) + Na 3 PO 4 (aq) Ca 3 (PO 4 ) 2 (s) + NaCl (aq) CLASSIFICATION Write the net ionic equation 1 Murov, S., and Stedjee, B., Experiments and Exercises in Basic Chemistry, 6 th Ed.,Hoboken, N.J., 2004, p Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 1

2 2. Get a wooden splint and prepare to light it on fire. In a small test tube containing 3 ml of 6 M hydrochloric acid (caution, corrosive), add a 1 cm 2 piece of zinc foil. If a gas evolves, point the test tube away from all people and quickly insert a wooden splint on fire into the test tube. Write the ionic equation for the 1 st reaction below. Zn (s) + HCl (aq) Zn Cl 2 (aq) + H 2 (g) H 2 (g) + O 2 (g) H 2 O (L) Write the net ionic equation for the 1 st reaction in #2 3. Heat a small test tube containing about 1 cm deep (1/4 ) of copper (II) hydroxide with a burner. Cu(OH) 2 (s) CuO (s) + H 2 O (g) 4. Mix 2 ml of 0.1 M calcium chloride with 2 ml of 0.1 M sodium carbonate. Write the products and balance the equation assuming it is a double replacement reaction. Save the contents for the next reaction. CaCl 2 (aq) + Na 2 CO 3 (aq) Write the net ionic equation 5. Centrifuge the mixture and decant (pour off) the supernatant, (the liquid above the precipitate). Add 1 ml of 1.5 M hydrochloric acid to the precipitate. Two reactions happen, first a double replacement and then a decomposition of a product, producing carbon dioxide and water. Complete the following equations. CaCO 3 (s) + HCl (aq) H 2 CO 3 (aq) Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 2

3 of the first reaction for # 5. Write the net ionic equation of the first reaction for #5. 6. The instructor will demonstrate the following reaction in order to conserve chemicals. Add about 1.5 g of solid ammonium chloride and 3.5 g of solid strontium hydroxide octahydrate in a 125 ml Erlenmeyer flask and mix vigorously for several minutes. No water is added. Note the odor, any sounds, and the flask temperature change. Two different types of reaction are taking place. You might want to try putting this mixture on a spatula and heating in a flame. There are two different reaction types taking place. Sr(OH) 2 8H 2 O (s) + NH 4 Cl (aq) SrCl 2 (aq) + NH 3 (g) + H 2 O (L) Briefly explain your choice of reaction types. 7. To a small test tube containing 3 ml of 0.1 M copper (II) sulfate add a piece of zinc foil. Wait several minutes before making your final observations. See if you can observe a change in the liquid color. Complete the reaction assuming it is a single replacement. CuSO 4 (aq) + Zn (s) if a reaction takes place. If No Apparent Reaction takes place, write NAR for the products above. Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 3

4 Write the net ionic equation for #7. 8. To a small test tube containing 3 ml of 0.1 M zinc sulfate add a 2 cm long piece of copper wire. Wait several minutes before making your final observations. See if you can observe a change in the liquid color. Complete the reaction assuming it is a single replacement. ZnSO 4 (aq) + Cu (s) (write NAR for no apparent reaction, if there is no sign of reaction). Write the net ionic equation (write NAR for no apparent reaction, if there is no sign of reaction). 9. Pour 2 ml of 6 M hydrochloric acid from a small test tube into a large test tube containing 4 ml of 3 M sodium hydroxide. Caution, both solution are corrosive to the skin and eyes. Complete the equation. HCl (aq) + NaOH (aq) Write the net ionic equation 10. Mix 1 ml of 0.1 M calcium chloride and 2 ml of 0.1 M sodium nitrate. Complete the equation. If No Apparent Reaction takes place, write NAR for the products above. CaCl 2 (aq) + NaNO 3 (aq) Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 4

5 11. In a small test tube held with a test tube holder, add a small amount of manganese (IV) oxide to 3 ml of 3% H 2 O 2 (hydrogen peroxide). The manganese (IV) oxide is a catalyst that speeds up the reaction of hydrogen peroxide. Catalyst speed up reactions without a chemical change in the catalyst substance. H 2 O 2 (aq) H 2 O (L) + O 2 (g) 12a. The waste in part 12 will go in the heavy metal waste container. Place 1 ml of 0.1 M silver nitrate into a small test tube and add 1 ml of distilled water and mix. Warning, silver nitrate will leave a black stain on your cloths and your skin. Get 1 ml of 0.5 M sodium bromide in a small graduated cylinder and add 4 drops of the sodium bromide to the silver nitrate drop by drop. Record your observation and centrifuge the contents of the tube for several minutes to clear up the liquid. Add 4 more drops of NaBr and record your observations. Centrifuge. Repeat until you get NAR. Dispose of the tube s contents in the heavy metal waste container, not down the sink. Wash it well. Complete the equation. AgNO 3 (aq) + NaBr (aq) Write the net ionic equation. Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 5

6 12. b. What happens when the first four drops of NaBr are added? What is the identity of the precipitate? What limits the production of product? What ions are in the solution above the precipitate? 12.c. As more drops and more drops of sodium bromide are added, did it ever stop making more product? Justify your answer. Use the ideas of a limiting reactant and an excess reactant to explain what has happened. What ions are in the solution above the precipitate when you get to where there is NAR when the sodium bromide is added? 12.d. What would happen to the solution in 12c if more if more silver nitrate was added? Lab_5_classification_chem_rxn_v6_S2015.docx Instructors Initials Page 6