Chemical Reactions Definitions and Formulas

Question 1

Ions in Aqueous Solutions

Answer 1

• Pure water does not conduct electricity
• Water can dissolve many things, referred to as the “Universal Solvent”
• Reactions taking place in water are called aqueous solutions.
• water becomes a conductor of electricity due to the production of ions

Question 2

Who is Svante Arrhenius?

Answer 2

• Swedish Chemist
• Proposed the idea that some substances dissociate into cations and anions when dissolved in water.
• His ideas are now known as the theory of electrolytic dissociation.

Question 3

Electrolyte

Answer 3

Substance that dissolves in water to give an electrically conducting solution.

e.g NaCl(s) → Na⁺(aq) + Cl^-(aq)

Most ionic compounds are strong electrolytes, but there are a few exceptions.

Question 4

Non-Electrolytes

Answer 4

Substance that dissolves in water to give a non-conducting or very poorly conducting solution.

e.g. C₁₂H₂₂O₁₁(s) + H₂O(l) → C₁₂H₂₂O₁₁(aq)

Question 5

How do you determine the strength of an electrolyte?

Answer 5

The strength of an electrolye depends on the extent of the dissociation or ionization in the solution.

Question 6

Dissociation

Answer 6

Seperation or splits apart as the salt dissolves

Question 7

Ionization

Answer 7

Formation of ions

Question 8

Strong electrolyte

Answer 8

an electrolyte that exists in solution almost entirely as ions

dissociates to a large extent; 70 to 100%

Question 9

Weak Electrolyte

Answer 9

dissolves in H₂O to give a small percentage of ions, about 1%

Question 10

Summary of Electrolytes

Answer 10

• Most ionic compounds are strong electrolye with a few exceptions
• Few molecular compounds are strong electrolytes
• Most molecular compounds are weak electrolytes or non-electrolytes
• Most organic compounds are molecular and non-electrolytes; however, carboxylic acids and amines are week electrolytes.

Question 11

Solubility

Answer 11

• Ability to dissolve in water varies according to the substance.
• Some substances are very soluble while others are insoluble.

Question 12

Describe reactions involving ions.

Answer 12

• Molecular equation
• Complete or total ionic equation
• Net Ionic equation

Question 13

Molecular equation

Answer 13

Chemical equation in which the reactants and products are written as if they were molecular substances, even though they may acutually exist in solution as ions.

Pb(NO₃)₂(aq) + 2K I(aq) 2KNO₃(aq) + PbI₂(s)

Question 14

Complete or total ionic equation

Answer 14

Chemical equation in which strong electrolytes such as soluble ionic compounds are written as seperate ions in the solution.

Pb²⁺(aq) + 2NO₃⁻(aq) + 2K ⁺(aq) + 2I⁻(aq) → 2K⁺(aq) + 2NO₃⁻(aq) + PbI₂(s)

Soluble solutions have (aq) subscripts and insoluble solid substances have (s) subscripts.

Question 15

Spectator Ions

Answer 15

• Ions the do not undergo any change in the reaction and appear on both sides of the equation.
• They are there to balance the charge

Question 16

Net ionic equation

Answer 16

• An ionic equation from which spectator ions have been canceled.
• Only the ions undergoing change are shown

—Pb²⁺(aq) + 2NO₃⁻(aq) + 2K ⁺(aq) + 2I⁻(aq) → 2K⁺(aq) + 2NO₃⁻(aq) + PbI₂(s)

to

Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s)

Question 17

Rules for writing Net Ionic Equations

Answer 17

1. Write strong electrolytes in their ionic form
2. Write weak electrolytes in molecular form
3. Write non-electrolytes in molecular form
4. Insoluble substances, solids or precipitates, and gases in their molecular form
5. Should only have substances that have undergone a chemical change.
6. Equation must be balances

Question 18

What are the 3 types of chemical reactions

Answer 18

There are three types:

1. Precipitaton reaction
2. Acid-base reeaction
3. Oxidation - Reduction reaction

Question 19

Precipitation Reaction

Answer 19

• When you mix two ionic substances and a solid precipitate result.
• Soluble reactants yield an insoluble product that drops out of the solution.
• The driving force for the reaction is the formation of the stable solid product which removes material from the aqueoaus solution

Question 20

Acid-Base reactions

Answer 20

An acid substance that involve the transfer of a proton (H+)

Question 21

Oxidation-Reduction reaction

Answer 21

Reaction that involves the transfer of an electron.

Question 22

Precipitate

Answer 22

• An insoluble solid compound formed durinf a chemical reaction in solution.
• To predict whether a precipitate will form on mixing aqueous solutions of two substances, you need to know the solubility of each potential product

Question 23

Solubility

Answer 23

1. How much of each compound will dissolve in given amount of solvent at a given temperature.
2. Low solubility in water
   
   • it is likely to precipitate from an aqueous solution
3. Hight solubility in water
   
   • no precipitate will form

Question 24

Exchange reaction

Answer 24

• Also known as metahesis reaction.
• reaction between two compounds that, when written as a molecular equation, appears to involve the exchange of parts between the two reactants.
• The two cations exchange partners
  
  • AB + CD → CB + AD
• Note: if an insoluble precipitate forms, then reaction is possible, if no precipitate, then no reaction.

Question 25

Acid-Base Reaction

Answer 25

* Important class of chemicals * acids: * have a sour taste * No feel * litmus change from blue to red * bases: * bitter taste * soapy feel. * litmus change from red to blue

Question 26

Acid-Base indicator

Answer 26

* A dye used to distinguish between acidic and basic solutions by means of the color changes it undergoes in these solutions. * Note: phenolphthalein sn indicator which is colorless in acid and pink in basic solution.

Question 27

pH value example

Answer 27

[![]() ](https://s3.amazonaws.com/brainscape-prod/system/cm/151/749/105/a_image_card.png?1436038711)

Question 28

Arrhenius Acid Definition

Answer 28

A substance that produces H+ when dissolved in water

Question 29

Arrenius base definition

Answer 29

Substance that produces hydroxide ions, OH^- when dissolved in water.

Question 30

Problems with Arrhenius acid-base definition

Answer 30

1. Reactions has to be in water 2. Some bases, such as NH3, ammonia and amines do not have hydroxides in their formula.

Question 31

Bronsted-Lowry Acid Definition

Answer 31

* the molecule or ion that donates a proton to another molecule or ion in a proton-transfer reaction * A proton H+ donor ![]()

Question 32

Bronsted-Lowry Base Definition

Answer 32

* Molecule or ion that accepts a proton in a proton-transfer reaction. * a H+ acceptor ![]()

Question 33

Bronsted-Lowry acid-base concept

Answer 33

![]()​ * Note that the acid becomes a base because it is lacking a proton and the base becomes an acid because it aquired a proton. * For simplicity, H+ is usually written but it is really H₃O⁺, called a hydronium ion.

Question 34

Hydronium Ion

Answer 34

* it is nothing more than a bare proton and does not exist by itself in aqueous solution * in water, it combines with a polar water molecule to form a hydrated hydrogen ion * the H+ is attached to to a polar water molecule forming a bond with one of the two pairs of unshared electrons. ![]()

Question 35

Neutralization Reaction

Answer 35

* Reaction of an acid and base to form an ionic compound (salt) and possibly water ![]() * Driving force of a neutrilization reaction is the ability of H+ ion and an OH- ion to react to form a molecule of unionized water. * If the spectator ions, in a neutralization reaction are soluble salts,they remain in the solution. * Evaporation of the solution to dryness yields the pure salts.

Question 36

What is the exception to the neutralization Reaction?

Answer 36

* Water is produced in most neutralization reactions * except for when the reaction of an acid is with a weak base (ammonia) ![]()

Question 37

Monoprotic acids

Answer 37

one acidic hydrogen atom per acid e.g. HCl, HNO₃, HCN, HBr,HI, HClO₄

Question 38

Polyprotic acids

Answer 38

* two or more acidic hydrogens per molecule. * e.g. H₂CO₃, H₃PO₄, H₂SO₄,etc . * They can form a series of salts with different amounts of base. * Some of the salts formed have hydrogen atoms so they are acidic salts and can undergo neutralization with bases. H₃PO₄(aq) + NaOH → NaH₂PO₄( aq) + H₂O(l) H₃PO₄(aq) + 2NaOH → Na₂HPO₄( aq) + 2H₂O(l) H₃PO₄(aq) + 3NaOH → Na₃PO₄( aq) + 3H₂O(l) * So salts, NaH₂PO₄ and Na₂HPO₄ are acidic salts.

Question 39

Acid-Base reactions with Gas Formation

Answer 39

* Some salts like carbonates, sulfites, and sulfides react with acid to produce gas. * Baking soda (NaHCO₃) reacts with an acid to produce carbonic acid, H₂CO₃, which decomposes to CO₂ and water. * The net ionic equations for some gas forming reactions are : * HCO₃⁻ + H⁺ →CO₂(g) + H₂O(l) * CO₃²⁻ + 2H⁺ → CO₂(g) + H₂O(l) * HSO₃⁻ + H⁺ → SO₂(g) + H₂O(l) * SO₃²⁻ + 2H⁺ → SO₂(g) + H₂O(l) * S²⁻ + 2H⁺ → H₂S(g) * HS⁻ + H⁺ → H₂S(g)

Question 40

Oxidation-reduction reactions

Answer 40

* Transfer of electrons, known as redox reactions * Oxidation * Loss of electrons (or increase of oxidation number) * Reduction * Gain of electrons (or decrease of oxidation number) * Mnenomic * LEO the lion goes GER * LEO: Lose electrons - oxidation * GER: Gain electrons - reduction * OIL RIG * OIL: Oxidation is loss of electrons * RIG: Reduction is gain of electrons

Question 41

Oxidation Number

Answer 41

* Actual charge on a monatomic ion or a hypothetical charge assigned to the atom in the substance by simple rules. * It is a way to keep track of electrons in a redox reaction * by comparing the oxidation number of an atom before and after reaction, we can tell whether it has gain or lost electrons. * For the oxidation number, the plus or minus sign is in front of the number to differentiate it from the electronic charge.

Question 42

Rules for assigning oxidation numbers

Answer 42

* Elements * is zero * Monatomic ions * equal to the charge on it * Oxygen * most compounds is -2, except for H₂O₂ where it is -1 * Hydrogen * most compounds is 1, except in binary compounds with a metal then it is -1 * Halogens * Flourine is -1 * Cl,Br,I is -1 in binary compounds, except when combined with a halogen above it or the other element is oxygen * Compounds and Ions * Algebraic sum in compounds is zero * Algebraic sum in a polyatomic ion is equal to the charge on the ion.

Question 43

Describing Oxidation-Reduction Reactions

Answer 43

* They occur simultaneously. * A half reaction tells you which is the oxidation and which is the reduction reaction. * It is possible to identify the reducing and oxidizing agent by the half reaction. ![]()

Question 44

Reducing Agent

Answer 44

* Causes reduction * loses one or more electrons * undergoes oxidation * oxidation number of atom increases

Question 45

Oxidizing Agent

Answer 45

* Causes oxidation * Gains one or more electrons * undergoes reduction * oxidation number of atom decreases

Question 46

Oxidizing and Reducing Agent

Answer 46

* The reducing agent is itself oxidized when it gives up electrons * The oxidizing agent is itself reduced when it accepts electrons. ![]()[![]() ](https://s3.amazonaws.com/brainscape-prod/system/cm/151/763/616/a_image_card.png?1436058025)

Question 47

What are the four common oxidation-reduction reactions?

Answer 47

1. Combination reaction 2. Decomposition reaction 3. Displacement reaction 4. Combustion reaction

Question 48

Combination Reaction

Answer 48

One of the oxidation-reduction reactions Two substances combine to form a third: 2H₂ + O₂ → 2H₂O

Question 49

Decomposition reaction

Answer 49

One of the oxidation-reduction reactions: One compound decomposes to give several substances 2HgO(s) → 2Hg(l) + O₂(g)

Question 50

Displacement reaction

Answer 50

* One of the oxidation-reduction reactions * An element displaces another element from a compound * Note: a metal will displace from solution the ions of any metal that lies below it in the activity series * e.g. a thermite reaction [![]() ](https://s3.amazonaws.com/brainscape-prod/system/cm/151/763/792/a_image_card.png?1436058666)

Question 51

Combustion Reaction

Answer 51

* One of the oxidation-reduction reactions * reaction with oxygen, with the rapid release of heat produces a flame. * CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂0(g) * Oxygen changes oxidation number from 0 to -2

Question 52

Balancing Simple Oxidation-Reduction reaction

Answer 52

* Charges must be balanced in as well as each element. * total increase in oxidation number equals total decrease in oxidation number

Question 53

Half-Reaction Method

Answer 53

* Identify oxidation/reduction half reactions by assigning oxidation numbers * Balance charge by adding electrons to the more positive side. * Right (product) side for the oxidation half reaction * Left (reactant) side for the reduction half reaction * Multiply by a factor to make the number of electrons equal. Cancel the electrons. Example: Mg(s) + N₂(g) → Mg₃N₂(s) 0 0 +2 -3 Balance oxidation half-reaction Mg(s) → Mg²⁺ + 2e^- N₂(g) + 6e^- → 2N^3- Need to multiply each half-reaction by a factor that will cancel the electrons 3(Mg(s) → Mg²⁺ + 2e^-) 1(N₂(g) + 6e^- → 2N^3-) 3Mg(s) + N₂(g) + 6e^- → 3Mg²⁺ + 2N^3- + 6e^- Get rid of the electrons: 3Mg(s) + N₂(g) → 3Mg²⁺ + 2N^3- 3Mg(s) + N2(g) → Mg₃N₂(s)

Question 54

Solution

Answer 54

* Reactions in a solution in faster * Parts of a Solution * Solute: substance dissolved or less abundant * Solvent: dissolving agent or more abundant * Concentrion: quantity of solute in a standard quantity of solution * Dilute: solute concentration is low * Concentrate: solute concentration is high

Question 55

Molar concentration

Answer 55

* also called Molarity (M) * is moles of solute dissolved in one liter of solution * Volume measurements are more convenient than mass measurements. Molarity can be used as a conversion factor. ![]()

Question 56

Dilution of Solutions

Answer 56

* Process of preparing a more dilute solution by adding solvent to a more concentrated one. * The addition of solvent does not change the amount of solute in a solution, but does change the solution concentration. * Moles of solute = molarity x Liters of solution * Formula: * M_initial x V_initial = M_final x M_final

Question 57

Quantitative analysis

Answer 57

Determination of the amount of a substance or species present in a material.

Question 58

Gravimetric Analysis

Answer 58

a type of analysis in which the amount of a species in a material is determined by converting the species to a product that can be isolated completely and weighed. Precipitation reactions are used in gravimetric analysis.

Question 59

Volumetric analysis

Answer 59

* Determining the amount of a substance by using the volume of another substance of know concentration required for a complete reaction. * Measures the volume of one reagent required to react with a measured mass or volume of another reagent. * based on titration.

Question 60

Titration

Answer 60

determining the concentration of a solution by allowing a carefully measured volume to react with a standard solution of another substance, whose concentration is known.