Unit 4 Lessons 21 & 22

Neutralization Reactions

• A neutralization reaction where adding acids and bases together neutralizes the solution producing an ionic salt compound and water
• Can be described as a double exchange where 2 compounds exchange cations

Ex: H2SO4 + Mg(OH)2 —> 2H2O + MgSO4
Practice Problems
7. C & D
8. B

Titration

    - procedure where a neutralization reaction is monitored with an indicator to get the unknown concentration
           - equivalence point is reached in a titration between a strong acid and a strong base , # of moles of H+ ions equals # of moles of OH- ions
Practice Problems
3) 1L of NaOH
5) a) acidic b) neutral c) basic

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Unit 4 Lesson 20

Dilution

This means that 8 is ten times more basic than 7 is one hundred times more acidic than 7.

You can add water to a solution to dilute it.

• In an acidic solution, adding water increases it's pH closer and closer to 7
• In a basic solution, adding water decreases the pH closer and closer to 7
• You can't reach a pH of 7 by simply diluting the solution with water and so you can't change an acid into a base or vice versa.

Practice Problems

5) because it was diluted so the pH decreased

7) a) .075 mol b) .068 M c) pH 1.17

 

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Unit 4 Lesson 19

[ H+] and pH

Acidity is determined by the concentration or Molarity of H+ ions n moles per liter. This concentration is symbolized by [H+].

The greater the concentration of H+ ions the lower the pH and it is more acidic.

The hydrogen ion concentration is directly related to the pH of the solution.

The pH number is equal to the exponent just without the negative. This is only true in scientific notation when the coefficient is 1.0.

pH is connected to [H+] through the logarithmic formula pH = -log[H+]

Bases' pH can also be determined because bases contain H+ concentrations. The H+ concentration in scientific notation and the exponent subtracted from 14 is the concentration of OH- ions.

Ex: water - [OH-] is 1.0 X 10^-7 and [H+] is 1.0 X 10^-7 because 7+7=14

Formula: [H+][OH-]= 1 X 10^-14

Practice Problems

3. a) pH 4 b) pH 12 c) pH 6

4. a) pH 2.85 b) pH 13.38 c) pH 7.22 d) pH .82

 

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Unit 4 Lesson 18

Acid-Base Theories

Acids

• Made up of main group nonmetals like carbon, oxygen, fluorine, and chlorine
• All have hydrogen
• Break apart to form one H+ and an anion

Bases

• Contain metal atoms and an hydroxide ion, OH-
• Except for hydroxides, the name isn't helpful to identifying them as bases

Changing definitions of acids and bases:

• Arrhenius definition- an acid is any substance that adds a hydrogen ion to a solution. A base is any substance that adds a hydroxide ion to a solution.
• Bronsted-Lowry definition- an acid is a proton donor and a base is a proton acceptor

Acids add H+ (one proton) to the solution

Bases add OH- to the solution

Strong Acids and Bases- dissociate completely in a solution to form only ions. They are good conductors of electricity.

Weak Acids and Bases- only partially dissociate in a solution. Less corrosive

Practice Problems
4. a) acid b) acid c) base d) acid e) acid f) acid g) acid h) base
6. a) 20 OH- ions

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Unit 4 Lesson 17

Acids and Bases

• Are corrosive and toxic
• Classified according to their observable behavior
• Change the color of indicators
• Water is not acidic or basic so it's neutral

Indicator- a molecular substance that changes color when it comes into contact with an acid or a base
The pH scale

The colors on the pH scale are associated with a "universal indicator" and every color has a specific number known as the pH.
Numbers on the left leading up to 7 are pHs relating to acids, 7 is neutral like water, and the numbers on the right after 7 refer to bases.
The further away from 7 on either side the potentially more toxic the acid or base would be.

Practice Problems
2. The pH scale is a number line that assigns numbers from 0-14 to acids or bases
5. a) acid b) base c) base d) neutral e) base

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Disappearing Spoon Chapter 10

The first thing talked about in this chapter is the fact that some elements do things we wouldn't expect them to do. For example, silver and copper are "self-sterilizing" which means that bacteria that comes into contact with them absorb their atoms and so their metabolisms are disrupted and they die. This explains why they are so commonly used in public places and why we have copper coated coins. Some are used for medicinal purposes like vanadium as a spermicide and gadolinium which is used in MRIs because gadolinium has the maximum number of unpaired electrons and so it is more magnetized than any other element. This combined with tumor targeting agents makes it easier to locate the tumor on the MRI. Also, gadolinium has the potential to fight cancer better than chemo because if gadolinium absorbs neutrons it turns radioactive and in a controlled situation, could destroy the tumor without destroying healthy cells around it. Louis Pasteur discovered in 1849 that almost all proteins in life forms are "left-handed" meaning they bend light clockwise when dissolved and that nature prefers to have molecules of all the same handedness and not a mixture of both. He also developed pasteurization and the rabies vaccine. In 1935 Gerhard Domagk used a red dye or Prontosil to cure his daughter of streptococcal and then Prontosil was examined by scientists at Pasteur Institute in France and found that mammal cells split it in two to create sulfonamide. Sulfonamide inhibits produstion of folic acid used in cells to replicate DNA and reproduction so while humans get folic acid from food, bacteria can't make their own so they can't reproduce. Domagk earned the Nobel Peace Prize in 1939 but was brutalized by Nazis and the Gestapo and later saved soldiers with his drugs, including Winston Churchill.

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Unit 4 Lesson 16

Mystery Solutions

Molarity can be used to identify a toxic substance.

• A substance dissolved in water adds mass to the solution
• 1 mol of a substance can have different molar mass than another
• Weighing different solutions with the same concentration can differentiate between them

Ex: 200mL 1.5M NaCl, 1M KCl, 1M CaCl2 which has the most mass?
NaCl - 58.5g –> .2L • 1.5 = .3mol • 58.5g = 17.64g
KCl - 74.5g –> .2L • 1 = .2mol • 74.5g = 14.9g

CaCl2 - 111g –> .2L • 1 = .2mol • 111 = 22.2g

CaCl2 has the most mass. This means the three solutions have the same concentration but since calcium chloride has the most mass then the heaviest solution will be the chloride solution, the second heaviest will be potassium chloride, and the least is sodium chloride.

 Practice Problem

7) a would weigh the most because it has the most amount of moles compared with mass

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Unit 4 Lesson 15

Preparing Solutions

You can find specific grams of solids to make specific molarities and find the concentration with all of the equations learned in this unit.

Ex: .01L of 0.5M of solution of NaBr. What is the mass?

Practice Problems

5) a. 10 L  b. .3 L  c. .18 L

7) 20g of glucose 

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Unit 4 Lesson 14

Molecular views

• The concentration of a solution doesn't change with the size of the sample
• Concentration is a measure of density of moles per unit of volume
• Total number of molecules does change with size
• Moles = k • volume of solution (k is the molarity) can calculate the # of moles in a sample
• When calculating the number of moles of particles in an ionic solution, it is necessary to take into account all the ions in the formula

Ex: ionic solution of NaCl with 1.0M in 1L means there are 1 mol of each NaCl
Ex: CaCl2 solution 100mL and 2.5M

• First find number of moles - 2.5 • .1L = .25 mol CaCl2
• This means that each ion has a mol of .25 so there is .25 mol of Ca and .5 mol of Cl because there are two of them
• In total .25 + .5 = .75 mol of ions

Practice Problems
1) Because volume and density/concentration are measured differently.
3) a. 1 L Glucose and sucrose because they has the same molarity and volume so the number of moles are the same. .
b. they all have the same concentration 1.0M
c. 1 L Sucrose because it has the same molarity and more volume than 500mL of sucrose and each molecule has more mass.

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Unit 4 Lesson 13

Solution Concentration

Solution - mixture of two substances that is uniform throughout

Solute - substance dissolved in a solution

Solvent - substance the solute dissolves in

Saturated solution - solution containing the maximum amount of solute for a given amount of solvent

Concentration - amount of solute dissolved in a specific volume

Can measure the concentration of a solution by finding the molarity

Molarity - concentration of a solution expressed in moles of solute per liter of solution

• Molecules move from areas of high concentration to areas with lower concentration

Practice problems
5) c,a,b

6) a(1M), b(2M), c(4.9M) 

9) A

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Unit 4 Lesson 12

Comparing Amounts

Using moles to compare toxic substances is preferred to using the masses because moles allow you to compare how many molecules of one toxic substance are equal to the mass of the number of molecules in a different toxic substance.

2 substances with = mass and = # of molecules and = toxicity can still differ in how much of which will effect you the most because the substance with the larger molar mass needs less of it to make up the same amount as the substance with a lower molar mass. This means the larger the molar mass the better.


Healthy effects due to toxic exposure depend on both LD50 and the amount of the substance.

Smaller lethal doses (LD50) means the more toxic the substance, but even if you don't consume the lethal dose, it doesn't mean there won't be any long term effects.

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Unit 4 Lesson 11

Mass-Mole Conversions

You have to convert mass into moles to find out the number of molecules/atoms

• Mass of the number of moles is atomic mass • number of moles
• # of mols of Carbon in 3.0 mol of C9H8O4?

- 27 mol of Carbon because 9 mol of carbon times 3.0 mol of the compound is 9 • 3 = 27 mol.
# of moles of H in 160g of NH3?

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Unit 4 Lesson 10

Molar Mass

Molar mass is the mass of 1 mol found on the periodic table as the atomic mass.

How many grams of Cl in 100g of CaCl?

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Unit 4 Lesson 9

Avogadro's Number

• 1 mol = 6.022 x 10^23

Scientific notation

• The decimal always has one number to the left
• Positive --> move the decimal point to the right
• Negative --> move the decimal point to the left

The mass of 1 mol of a substance is called the molar mass

• Atomic mass given on the periodic table is = to the mass of 1 mole of atoms of the element in grams
• Molar mass allows you to convert between moles of atoms and grams of atoms

Ex:

Practice Problems

4) a. 14  b. 20.1797  c. 35.5  d. 63.5

5) a. Carbon  b. iron  c. Gold  d. Gold

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Unit 4 Lesson 8

Counting by Weighing

Weighing really lightweight objects to help find the mass is a lot more difficult and less accurate than when weighing heavier objects. To accurately weigh one you must:

• Weigh a group of the identical objects
• Divide that weight by the number of objects
• Gives an average weight for one

Knowing the average weight of one object means you can pretty accurately determine the number of the objects in a large group by weighing the larger group and dividing that by the average weight.

Percent Error

Percent error allows you to see how close your answer is to the actual answer.

Formula: |(observed value - actual value)| • 100

actual value

 Practice Problems
4) the rice because rice is generally smaller than beans so more of them would be needed to equal 50 grams of beans.
5) 740 marbles has more mass because they are bigger and so take up more mass

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Unit 4 Lesson 7

Lethal Dose

Toxicity

Lethal Dose (LD50) - amount of an ingested substance that kills 50% of a test sample of animals.

• Expressed in mg/kg of body weight
• 1 kg = 2.2 lbs

Toxicity depends on 2 qualities: amount of substance and mass of the organism

Everything can be toxic if you take in enough of it

The smaller the LD50 the more potentially dangerous

Practice Problems

2) toxicity depends on weight because the more someone weighs, the more of the toxic substance they need to be as affected as a lighter person.

 

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