Chapter 9 chemistry note

·         Isotopes are atoms of the same element that have different numbers if neutrons.

·         Most naturally occurring isotopes up to atomic number 19 have stable nuclei.

·         Elements with atomic numbers 20 and higher usually have one or more isotopes that have unstable nuclei, in which nuclear forces cannot offset the repulsions between the protons.

·         An unstable nucleus is radioactive, which means that it spontaneously emits small particles of energy, called radiation, to become more stable.

·         Radiation may take the form of particles such as alpha and beta particles, positrons, or pure energy such as gamma rays.

·         An alpha particle is identical to a helium (He) nucleus, which has 2 protons and 2 neutrons.

·         An alpha particle has a mass number of 4, an atomic number of 2, and a charge of 2+.

·         A beta particle is an electron that is emitted when a neutron in an unstable nucleus changes to a proton and electron. A beta particle has a charge of 1- and a mass number of 0.

·         A positron has a positive 1+ charge with a mass number of 0, which makes it similar to a beta particle.

·         Gamma rays are high energy radiation, released when an unstable nucleus under-goes a rearrangement of its particles to give a more stable, lower energy nucleus.

·         When radiation strikes molecules in its path, electrons may be knocked away, forming unstable ions.

·         The cells most sensitive to radiation are the ones undergoing rapid division- those of the bone marrow, skin, reproductive organs, and intestinal lining, as well as all cells of growing children.

·         Cancer cells are another example of rapidly dividing cells.

·         Alpha particles, the heaviest of the radiation particles, travel only a few centimeters in the air before they collide with air molecules, acquire electrons, and become helium atoms. A piece of paper, clothing, and our skin provide protection against alpha particles.

·         Beta particles move much faster and farther than alpha particles, traveling as much as several meters through the air. They can pass through paper and penetrate up to 4 to 5 mm into body tissue.

·         Gamma rays travel great distances through the air and pass through many materials, including body tissues. Because gamma rays can penetrate so deeply, exposure to these rays is extremely dangerous.

·         Symbols:

o   Alpha: α               Mass number:4                Charge: 2+

o   Beta: β                   Mass number: 0               Charge: 1-

o   Positron: β⁺                         Mass number: 0               Charge 1+

o   Gamma Ray: γ      Mass number: 0               Charge: 0

o   Proton: p               Mass number: 1               Charge: 1+

o   Neutron: n             Mass number: 1               Charge: 0

·         When radiation strikes molecules in its path, electrons may be knocked away, forming unstable ions.

·         The cells that are most sensitive to radiation are the ones undergoing rapid division: bone marrow, skin, reproductive organs, and intestinal lining, as well as all cells of growing children.

·         Alpha particles, the heaviest of the radiation particles, travel only a few centimeters in the air before they collide with air molecules, acquire electrons, and become helium atoms. Paper, clothing, and skin protect us from alpha particles. Dangerous if inhaled due to high ionization.

·         Beta particles move much faster and farther than alpha particles, traveling as much as several meters through the air. They can pass through paper and penetrate as far as 4-5 mm into the body tissue. External exposure can burn the surface of the skin. Use heavy clothing such as lab coats and gloves.

·         Gamma rays travel great distances through the air and pass through many materials including body tissues. Exposure is extremely hazardous, lead or concrete are required to stop them.

·         When a nucleus spontaneously breaks down by emitting radiation, the process is called radioactive decay.

o   Radioactive nucleus ànew nucleus + radiation (α β β+ γ)

§  It’s shown as a nuclear equation using the symbols for the radioactive nucleus, the new nucleus, the new nucleus, and the radiation emitted.

·         In a nuclear equation, the mass numbers and the atomic numbers must balance so the number of protons and neutrons are equal on both sides. It is often a change in the number of protons, which gives a different element.

·         An unstable nucleus undergoes alpha decay by emitting an alpha particle. Because an alpha particle consists of 2 protons and 2 neutrons, the mass number decreases by 4, and the atomic number decreases by 2.

Chapter 8 chemistry note

·         The term acid means sour. Acids are substances that produce H+ ions when they dissolve in water. Their formulas start with H and the suffixes are –ic or –ous. An acid can donate a proton. The chemical that remains after the proton is donated is a base.

Formula	Name	Strong?
HCl	hydrochloric acid	yes
HBr	hydrobromic acid	yes
HI	hydroiodic acid	yes
HF	hydrofluoric acid	no
HNO3	nitric acid	yes
H2SO4	sulfuric acid	yes
H3PO4	phosphoric acid	no
CH3COOH	acetic acid	no

·         Bases are ionic compounds that dissociate into a metal ion and hydroxide ions (OH-) when they dissolve in water. Their formulas end with OH and that last word in the formula is hydroxide.

Formula	Name	Strong?
NaOH	sodium hydroxide	yes
LiOH	lithium hydroxide	yes
KOH	potassium hydroxide	yes
Mg(OH)2	magnesium hydroxide	no
Ca(OH)2	calcium hydroxide	no
Al(OH)3	Aluminum hydroxide	no

·         When a base accepts a proton, it becomes an acid because it now has a proton that it can donate. And when an acid donates a proton it becomes a base, because it now has room to accept a proton.

original acid	conjugate base
HNO3	NO3-
H2O	OH-
H3O+	H2O
H2SO4	HSO4-
HBr	Br -
HCO3-	CO32-

original base	conjugate acid
OH-	H2O
H2O	H3O+
HCO3-	H2CO3
SO42-	HSO4-
ClO4-	HClO4

·         When an acid gives up its proton, what remains is called the conjugate base of that acid. When a base accepts a proton, the resulting chemical is called the conjugate acid of that original base. HF and F^- are a conjugate acid-base pair. H₂O and H₃O⁺ are a conjugate pair, where H₃O⁺ is the acid and H₂O is the base.

equation

H2SO4 + H2O HSO4- + H3O+

HCl + OH- Cl- + H2O

HCl + NH3 Cl- + NH4+

NH3 + H2O NH4+ + OH-

·         The strength of an acid or a base in water is determined by its ability to donate or accept protons.

·         Strong acids are examples of strong electrolytes because they donate protons so easily that their disassociation in water in virtually complete. Weak acids don’t donate as many protons.

·         Most acids are weak acids, which mean that they are also weak electrolytes. They disassociate slightly in water, which means that only a small percentage of the dissolved molecules donate H+ to H ₂O.

·         Citric acid is a weak acid found in fruits and fruit juices such as lemons, oranges, and grapefruit.

·         Vinegar contains another weak acid known as lactic acid.

·         As strong electrolytes, the Arrhenius bases are strong bases that disassociate virtually completely in water. Because these strong bases are ionic compounds, they disassociate in water to give an aqueous solution of a metal ion and hydroxide ion. Strong bases accept protons readily.

·         Weak bases are weak electrolytes that are poor acceptors of protons and produce very few ions in solution. A typical weak base, ammonia, NH₃, is used in cleaning products. In an aqueous solution of NH₃, only a few molecules accept protons to form ammonium hydroxide.

·         Water acts as an acid or a base. It is a base when one water molecule donates an H+ to another water molecule.

·         When acid mixes with H2O it ALWAYS makes H3O and the H comes off of the front of the acid formula.

·         When writing formulas for acids- check the polyatomic table, as many acids come from this, and the H can be added to it and the numbers switched if need be.

·         When asked to write the formula and name of the conjugate base for an acid, take out the H and add –ide.

o   HF = F-, fluoride ion

o   H₂O = OH-, hydroxide ion

o   H₂CO₃ = HCO₃, bicarbonate ion

·         Every time a H+ is transferred between two water molecules, the products are one H₃O and one OH-. Experiments have determined that, in pure water, the concentrations of H3O+ and OH- at 25C are each 1.0 X 10^-7 M.

·         Square brackets around the symbols indicate their concentrations in moles per liter (M). [H3O+] = [OH-] = 1.0 X 10^-7 M.

·         When we multiply these concentrations, we obtain the ion-product constant of water, K_w, which is 1.0 X 10^-14. The concentration units are omitted in the K_w value.

·         The K_w value of 1.0 X 10^-14 is important because it applies to any aqueous solution: all aqueous solutions have H3O+ and OH-.

·         No matter the amount of acid and base, it always equals 1 X 10^-14

·         Any aqueous solution that’s an acid, base, or neutral, the product is equal to K_w.

·         On the pH scale, a number between 0 and 14 represents the H₃O+ concentration for most solutions.

·         A neutral solution has a pH of 7.0      [H₃O+] = 1 X 10^-7

·          An acidic solution has a pH < 7.0       [H₃O+] > 1 X 10^-7

·         A basic solution has a pH > 7.0            [H₃O+] < 1 X 10^-7

·         pH  = -log[H₃O+]

·         The negative powers of 10 in the molar concentrations are converted to positive numbers. For example 1 X 10^-3 has a pH of 3.

·         Because the pH is a log scale, a change of one pH unit corresponds to a ten-fold change in [H3O+]. For example, a solution with a pH of 2 has a [H3O+] 10 times higher than a solution with a pH of 3 and 100 times higher that a solution with a pH of 4.

·         As the pH decreases as the [H₃O+] increases.

·         Typical reactions of acids and bases include the reactions of acids with metals, bases, and carbonate or bicarbonate ions.

·         Acids react with certain metals to produce hydrogen gas (H₂) and a salt, which is an ionic compound that does not contain H+ or OH-.

·         Neutralization is a reaction between an acid and a base to produce a salt and water. In the reaction, the H+ of an acid that can be strong or weak and the OH- of a strong base combine to form water as one product. The salt that is usually soluble is the cation from the base and the anion from the acid.

·         ****Watch for polyatomics!!!************************When the elements combine don’t forget to switch their number according to the periodic table***************************

·         In a neutralization reaction, one H+ always combines with one OH-.

·         Writing the balanced equation for the reaction of HCl

o   Al:

§  Write the reactants and products: when a metal reacts with an acid, the products are H₂ gas and a salt.

Al + HCl à H₂ + salt

§  Determine the formula of the salt: when Al dissolves, it forms Al^3+, which is balanced by 3 Cl- from HCl.

Al + HCl à H₂ + AlCl₃

§  Balance the equation

2Al + 6HCl à 3H₂ + 2AlCl₃

·         When a carbonate (CO­₃)  reacts with an acid, the products are CO₂, H₂O, and a salt (GAS + WATER + SALT)

o   K­₂CO₃ + HCL à CO₂ + H₂O + KCl

o   *****Whenever you see CO₃ in a balancing problem, automatically take out CO₂ and H₂O first, then figure out the rest.

·         When H­ is combined with (OH) it makes water (H₂O)

·         Titration is used to find the molarity of a solution in which we neutralize an acid sample with a known amount of base.

·         A buffer is a solution that maintains pH by neutralizing added acid or base. For example, blood contains buffers that maintain a constant pH of 7.4.

·         Buffers consist of nearly equal concentrations of a weak acid and it’s conjugate base or a weak base and it’s conjugate acid.

·         To indicate whether a solution is acidic, basic, or neutral (calculating the pH):

o    Of a solution [H₃O+] : –log (place the scientific notation problem here) = <7 is acidic, >7 is basic, =7 is neutral

o   Of a solution [OH-]: first divide the solution problem into (10^-14), then use the –log formula to complete it

§  [OH-] = 8.0 X 10^-3 M

·         (10^-14)/(8.0 X 10^-3) = 1.25 X 10^-12; -log (1.25 X 10^-12) = 11.9

·         If the pH is given, the [H₃O+] is 1 X 10^pH

Chapter Seven chemistry note

·         A solution is a homogeneous mixture in which one substance called the solute is uniformly dispersed and the other substance is called the solvent. The solute and solvent do not react with each other and can be mixed in varying proportions.

·         Sugar in sugar water is the solute and water is the solvent. Carbon dioxide in soda is the solute and the liquid is the solute.

·         Hydrogen bonds occur between molecules where a partially positive hydrogen is attracted to the strongly electronegative atoms of O, N, or F in other molecules.

·         In water, hydrogen bonds are formed by the attraction between the oxygen atom of one water molecule and a hydrogen atom in another molecule.

·         The attractive forces of several water molecules provide the energy to break the ionic bonds between Na and Cl ions in the NaCl crystal.

·         Solutes can be classified by their ability to conduct an electrical current. When solutes called electrolytes dissolve in water, they separate into ions, which are able to conduct electricity.

·         Non electrolytes will form but won’t form ions.

·         Solubility is used to describe the amount of a solute that can dissolve in a given amount of solvent

·         If a solute readily dissolves when added to the solvent, the solution does not contain the maximum amount of solute. This is unsaturated.

·         Saturated means that the liquid has dissolved all the solute that it can.

·         The solubility of most solids is grater as temperature increases, which means that solutions usually contain more dissolved solute at higher temperatures

·         The amount of solute dissolves in a certain amount of solution is called concentration of the solution.

o   Concentration  = amount of solute/amount of solution

·         Because the volumes of liquids or gases are easily measured, the concentrations of their solutions are often expressed as volume percent.

o   Volume percent  (% v/v)= volume of solute/volume of solution X 100%

·         A mass/volume percent is calculated by dividing grams of the solute by the mL of the solution and multiplying 100

o   Mass/volume percent (%m/v) = grams of solute/mL of solution X 100%

·         Molarity is the concentration that states the number of moles of solute in exactly 1L of solution.

o   Molarity (M) = moles of solute/liters of solution

·         Dilution is the process when a solvent is added to a solution in which increases the volume and decreases the concentration

o   C₁V₁ = C₂V₂

·         When the concentration is given as molarity (M), the moles of the solute are obtained from the volume (L) and the molarity

o   Moles of solute = molarity (moles/L) X volume (L)

·         Isotonic solutions exert the same osmotic pressure as body fluids; NaCl and D5 are the most isotonic

·         Hypotonic has a lower solute concentration so it the solution can flow into cells by osmosis, possible causing the cells to burst.

·         Hypertonic has a high solute concentration, so the water will be drawn to it, causing the cells to shrink.