Reactions (Chapter 4) Notes 2016.notebook. October 14, Chemical Reactions. Chapter 4 Notes. Oct 21 8:44 AM. Oct 22 10:14 AM

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Bennett Gibbs
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1 Chemical Reactions Chapter 4 Notes Oct 21 8:44 AM Oct 22 10:14 AM 1

2 There are several things to keep in mind writing reactions and predicting products: 1. States of matter of elements/compounds 2. Diatomics and elements that are similar 3. Balance reactions 4. Solubility rules (single/double replacement) 5. Net Ionic Equations Oct 21 8:53 AM Types of reactions Synthesis reactions: when two or more elements or compounds combine to form one new compound A + B > AB Decomposition reactions: one compound breaks down into two or more elements or compounds AB > A + B Single Replacement When an element replaces a like element in a compound AB + C > AC + B Double Replacement When an element in a compound replaces a like element in a compound AB + CD > AD + CB Combustion When an element or compound reacts with oxygen. We will primarily describe this type of reaction as a hydrocarbon molecule reacting with oxygen to form carbon dioxide and water C x H y O z + O 2 > H 2 O + CO 2 Oct 21 8:45 AM 2

Solubility and Hydration Solubility (miscibility): Ability to dissolve in water Hydration: when water surrounds an ion so that the "negative" end is attracted to the positive ion and the "positive"

3 Solubility and Hydration Solubility (miscibility): Ability to dissolve in water Hydration: when water surrounds an ion so that the "negative" end is attracted to the positive ion and the "positive" end is attracted to the negative ion Oct 12 2:38 PM ` Net Ionic Equations Net Ionic Equations: an equation that only shows the ions that are reacting and removes all species that are spectator ions. Potassium iodide and lead (II) nitrate solutions are mixed together in a beaker Step 1: Write out the reaction with proper states of matter Step 2: separate aqueous compounds into ions Step 3: Cross out ions that are the same on both sides of the equation. (Spectator ions) Step 4: Rewrite the equation so that only ions that are reacting are shown Oct 21 9:25 AM 3

4 Net Ionic Equations A 0.2 M potassium hydroxide solution is titrated with a 0.1 M nitric acid solution. A strip of magnesium metal is placed in a solution of iron(ii) chloride. A solution of nickel(ii) bromide is added to a solution of potassium hydroxide. Zinc metal is placed in a solution of copper(ii) sulfate. Sulfur in its standard state is burned in air A solution of potassium carbonate is added to a solution of strontium chloride. Oct 12 3:00 PM Neutralization Reaction: A double replacement reaction in which an acid reacts with a base to produce water and a salt. HCl(aq) + NaOH(aq) > H 2 O(l) + NaCl(aq) (Neutral does NOT mean the ph is 7!!!) Oct 12 3:14 PM 4

5 Binary acids: An acid where the acidic proton (Hydrogen) is connected to just one other type of atom HCl, H 2 S, H 3 N Oxyacids: An acid where the acidic proton (Hydrogen) is connected to an oxygen atom HClO 3, HNO 3, H 2 SO 4 Oct 12 3:14 PM Strong Acid: Ionize completely in water Strong Acid List (All other acids are considered weak) HCl HBr HI HClO 4 HIO 4 HClO 3 HNO 3 H 2 SO 4 Monoprotic acid an acid having one proton (H + ) Diprotic acid an acid having two protons (H 2 SO 4 is a strong acid, however HSO 4 is a weak acid. Oct 19 8:32 AM 5

6 Strong Base:Dissociates completely in water NaOH < > Na + + OH Strong bases: All group 1A hydroxides are strong bases as well as Ca(OH) 2, Ba(OH) 2, and Sr(OH) 2 Oct 19 8:35 AM ph Scale: a convenient way to present solution acidity (or alkalinity) based off of a log base 10 scale. ph = log[h + ] [H + ] = 1.0x10 7 M ph = 7.00 Note: the number of sig figs in the original number is how many decimal places are in the log K w = [H + ][OH ] pk w = ph + poh ph + poh = 14 Oct 19 8:35 AM 6

7 Titrations: Analysis technique used to determine the amount of acid or base in a solution. It involves a solution of known concentration (the titrant) delivered from a buret into the unknown solution until the substance being analyzed is just consumed. This is called the equivalence point and is often signaled by the color change of an acid base indicator (end point). Oct 19 8:39 AM Oct 19 8:41 AM 7

8 Acid Base Indicators: a substance that marks the end point of a titration by changing colors. End point should be around the same as the equivalent point but we want the color change of the indicator to be around the same ph as the equivalence point. Oct 19 8:41 AM A 0.339M HCl solution is used to titrate 45.3 ml solution of sodium hydroxide. If 34.6 ml of the HCl is needed to reach the halfway point, what is the ph at the halfway point (use the reaction as a guide for this) Draw a particulate representation of the halfway point What volume of HCl is needed to reach the equivalence point. What is the ph at the equivalence point What is the molarity of the NaOH solution Oct 19 8:41 AM 8

9 Redox Reactions Oxidation Reduction Reactions (Redox): reactions in which elements' oxidation states are changed through the transfer of electrons Oxidation: The process in which electrons are lost and the oxidation state becomes more positive Reduction: The process in which electrons are gained and the oxidation state becomes more negative LEO GER Oct 21 10:03 AM OIL RIG Redox Reactions All synthesis, decomposition, combustions, and single replacement reactions are considered simple redox reactions Oxidation Numbers: A way to assign the electrons within a substance. For binary ionic compounds, this is simply the charge H 2 + O 2 > H 2 O Oct 22 9:12 AM 9

10 Redox Reactions H 2 + O 2 > H 2 O Step 1: Write out the half Reactions Step 2: Balance charges with electrons and assign each half reaction as either oxidation or reduction Step 3: Balance electrons Step 4: Add together and cancel out like terms: Oct 22 9:12 AM Redox Reactions Magnesium burns in air Propane is burned completely in excess oxygen gas. Copper is added to a solution of silver nitrate A piece of calcium metal is oxidized by adding it to a solution of copper (II) chloride Hydrogen chloride gas is oxidized by oxygen gas Oct 22 9:12 AM 10

11 Complex Redox Some redox reactions are more complicated because they occur in acidic and basic solutions. MnO 4 (in acidic solution) > Mn +2 + H 2 O MnO 2 (in acidic solution) > Mn +2 + H 2 O MnO 4 (in neutral or basic solution) > MnO 2 Cr 2 O 7 2 (in basic solution) > CrO H 2 O CrO 4 2 (in basic solution) > CrO 2 + H 2 O HNO 3 (Concentrated) > NO 2 + H 2 O HNO 3 (dilute) > NO + H 2 O H 2 SO 4 (Hot, concentrated) > SO 2 + H 2 O Free Halogens > Halide Ions H 2 O 2 (in acidic Solution) > H 2 O H 2 O 2 (decomposes) > H 2 O + O 2 HClO 4 > Cl + H 2 O Oct 22 9:27 AM Acidic Complex Redox Copper Metal is added to dilute nitric acid Cu + NO 3 > Cu +2 + NO Step 1: Write out the half Reactions Step 2: Balance all elements, except for oxygen and hydrogen in each half reaction Step 3: Balance the oxygen with water Step 4: Balance the Hydrogen with H+ ions Step 5: Balance the electrons Step 6: Equal electrons Step 7: Combine and simplify Oct 22 9:27 AM 11

12 Acidic Complex Redox ClO 3 + SO 2 > SO 42 + Cl Oct 22 9:57 AM Basic Complex Redox Cr +3 + ClO 3 > CrO Cl Balance exactly like you did the acidic solutions except when you add the hydrogen ions you will add hydroxide ions to cancel them out. Oct 22 9:57 AM 12

13 ` Basic Complex Redox Br + MnO 4 > MnO 2 + BrO 3 CN + IO 3 > I + CNO Oct 22 9:57 AM Acidic Complex Redox Acidic Cr 2 O 72 + Fe 2+ > Cr 3+ + Fe 3+ Zn + NO 3 Zn NH 4 Cr 2 O 72 + Fe 2+ > Cr 3+ + Fe 3+ Cu + SO 42 > Cu 2+ + SO 2 Basic SO Cr 2 O 7 2 > Cr 3+ + SO 4 2 Cr 3+ + H 2 O 2 > CrO H 2 O Br + MnO 4 > MnO 2 + BrO 3 Nov 6 12:36 PM 13

14 Oct 14 11:22 AM 14

7/16/2012. Chapter Four: Like Dissolve Like. The Water Molecule. Ionic Compounds in Water. General Properties of Aqueous Solutions

7/16/2012. Chapter Four: Like Dissolve Like. The Water Molecule. Ionic Compounds in Water. General Properties of Aqueous Solutions General Properties of Aqueous Solutions Chapter Four: TYPES OF CHEMICAL REACTIONS AND SOLUTION STOICHIOMETRY A solution is a homogeneous mixture of two or more substances. A solution is made when one substance