CHEM115 Lab#3: Chemical Reactions and Equations PDF

CHEM115 Lab#3: Chemical Reactions and Equations Activities Supplies Test tubes A. Sodium and water (Demo)...

CHEM115 Lab#3: Chemical Reactions and Equations Activities Supplies Test tubes A. Sodium and water (Demo) Test tube rack Matches and wood splint Na (s) + H2O (l) NaOH(aq) + H2 (g) Chemical B. Zinc and copper(II)sulfate Na (s) , Zn (s) , Mg (s) 1.0M CuSO4 & 1.0M, HCl1.0M C. Metals (Zn & Mg) reactions with HCl. 0.1M solutions of CaCl2 Na3PO4 BaCl2 Na2SO4 FeCl3 KSCN D. Reaction of ionic compounds Phenolphthalein Na2CO3 (s) CaCl2 (aq) + Na3PO4 (aq) Ca3(PO4)2 (s) + NaCl (aq) BaCl2 (aq) + Na2SO4 (aq) BaSO4 (s) + NaCl (aq) Cleaning FeCl3 (aq) + KSCN (aq)  Fe(SCN)3 (aq) + KCl(aq) Clean all test tube twice in the chemical waste then use brush with soup then rinse E. Sodium carbonate and HCl Waste disposal All chemical goes to chemical waste beaker then to heavy metals waste container  CHEM115 Lab#3: Chemical Reactions and Equations Drop and Dropping bottles  CHEM115 Lab#3 Chemical Reactions and Equations Drop and Dropping bottles The drop is an approximated unit of measure of volume, the amount dispensed as one drop from a dropper or drip chamber. It is often used in giving quantities of liquid drugs to patients, and occasionally in cooking and in organic synthesis. The abbreviations gt. or gtt. come from the Latin noun gutta ("drop"). The volume of a drop is not well defined: it depends on the device and technique used to produce the drop, on the strength of the gravitational field, and on the viscosity, density, and the surface tension of the liquid.  CHEM115 Lab#3: Chemical Reactions and Equations Symbols in Chemical Equations Symbol Translation Yield or produces (separates reactants from products) + Reacts with or forms alongside (separates two or more reactants or products) ∆ Reaction mixture is heated (written over the arrow) NR No reaction takes place when reactants are mixed (s) Pure substance (reactant or product) is a solid (l) Pure substance (reactant or product) is a liquid (g) Pure substance (reactant or product) is a gas (aq) Aqueous solution (reactant or product is dissolved in water) Catalyst – a substance needed to initiate a reaction (formula is written over the Cat arrow)  CHEM115 Lab#3: Chemical Reactions and Equations Type of General Description and Example(s) Reaction Two reactants combine to form a single product. The reactants may be elements or compounds. Also called a synthesis reaction. Combination Zn(s) + I2 (s) → ZnI2 (s) CaO(s) + H2O (l) → Ca(OH)2 (s) One reactant, a compound, breaks down to give two or more products. Decomposition 2H2O2(aq) → 2H2O (l) + O2(g) An element reacts with a compound and replaces one of the elements in the compound. Metals replace hydrogen or other metals, nonmetals replace nonmetals. Single Zn(s) + 2HCl (s) → H2 (g) + ZnCl2 (aq) Replacement Cu(s) + 2AgNO3 (aq) → 2Ag (s) + Cu(NO3)2 (aq) Cl2(aq) + 2NaI (aq) → I2 (aq) + 2NaCl (aq) Two ionic compounds (or compounds that break apart to form ions in solution) exchange ions to form new compounds. Examples include precipitation reactions (driving force is formation of a precipitate), acid-base reactions (driving force is formation of water), and gas-forming reactions (driving force is evolution of a gas) Double Replacement NaCl(aq) + AgNO3 (aq) → AgCl (s) + NaNO3 (aq) (precipitation) H2SO4(aq) + 2NaOH (aq) → Na2SO4 (aq) + H2O (l) (acid-base) Na2SO3(aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + SO2 (g) (gas forming) A compound burns in the presence of oxygen, producing energy in the form of heat and light. The combustion of Combustion organic compounds produces carbon dioxide and water. C4H8(l) + 6O2 (g) → 4CO2 (g) + 4H2O (g)  CHEM115 Lab#3: Chemical Reactions and Equations How to Know if a Chemical Change Has Occurred? Color Changes When the statue was originally assembled, it was a dull brown color, reflecting the natural color of its copperplates. Over the next 30 years, though, it slowly turned to the green color you see today. What happened? Was it magic? No, It was science!! A natural weathering process — called oxidation, took place when air and water reacted with the copper plates. Over time, the weathering of the copper created a thin layer of copper carbonate called a patina. Although some people were worried that the changing color of the statue meant it was decaying, the patina actually protects the copper underneath from further corrosion.  CHEM115 Lab#3: Chemical Reactions and Equations How to Know if a Chemical Change Has Occurred? Precipitates forming  CHEM115 lab#3: Chemical Reactions and Equations How to Know if a Chemical Change has Occurred? Temperature Changes (Releasing or Absorbing heat) Production of Light When energy is released due to a chemical change it sometimes creates a light source. This type of chemical reaction tends to occur in combustion reactions such as a fire or burning process. Man-made examples of a light being emitted due to a chemical change include fireworks, exploding in the sky and creating a colorful display. Natural examples include fireflies, which use a chemical reaction in their bodies to produce light. So many candles are made from “paraffin wax” which has the chemical formula C25H52. When paraffin comes into contact with oxygen with enough energy, it burns completely and becomes water and carbon dioxide. The fire is a result of this reaction happening very quickly and is known as combustion  CHEM115 lab#3: Chemical Reactions and Equations How to Know if a Chemical Change has Occurred? Gas Production Some chemical changes produce a gas as a product of a reaction. The electrolysis of water, for example, is a decomposition reaction that breaks water into hydrogen and oxygen gas. You can tell this change has occurred when bubbles of gas arise from the electrodes. In the single replacement reaction between zinc metal and sulfuric acid, zinc sulfate and hydrogen gas are formed. You can tell hydrogen gas is present by lighting a splint and placing it inside the test tube after the reaction occurs; the splint will pop because the flame ignites the hydrogen.  CHEM115 lab#3: Chemical Reactions and Equations How to Know if a Chemical Change has Occurred? Change in Smell or Taste Each chemical compound has its own distinct smell or taste. When the compound changes after a chemical reaction, the taste or smell of the compound changes as well. An example of this is when fresh food that once smelled delicious slowly spoils and smells rotten. This bad smell sends a warning signal to the brain that tells the person not to eat the food. Volume Change Each chemical compound has a specific density. If the chemical compound changes due to a chemical reaction, the density changes as well. This causes the volume of the substance to recede or expand during the reaction process. If the volume changes too rapidly, it may cause an explosion. An example of a volume change due to a chemical reaction is when gas bubbles form in magma inside a volcano and expand too rapidly, leading to a volcanic eruption CHEM115 lab#3: Chemical Reactions and Equations How to Know if a Chemical Change has Occurred? Reactivity series table