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Chemistry 101 Lab Final Notes

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Yoram Apelblat

Chapter 7, section 1: Spectrums  - Frequency = # of cycles it under goes per second (Hz) - Wavelength = the distance between any point on a wave and the corresponding point on the next crest (m or nm) - Speed = the distance it moves per unit time (m/s), the product of its frequency (cycles per second), and wavelength (m/cycle)  C = 3.00 x 10 m/s  C =    Since the product of wavelength x frequency is constant, they have a reciprocal relationship ( ) or ( ) - Amplitude = height of the crest (or depth of the trough)  Higher amplitude = more intense/bright  Lower amplitude = less intense/bright Electromagnetic Spectrum  Red = ~750nm Orange/yellow = ~600nm Green = ~500nm Violet = ~400nm - Light of a single wavelength is called monochromatic (“one color”) - Light of many wavelengths is called polychromatic Refraction and Dispersion: - When a light passes from one medium into another, the speed of the wave changes  refraction - If a wave strikes the boundary between media (between air and water), at an angle other than 90, the change in sped causes a change in direction and the wave continues at a difference angle  Angle of Refraction - White light separates into its component colors when it passes through a prism because each incoming wave is refracted at a slightly different angle  Dispersion - When a wave strikes the edge of an object, it bends around it  diffraction Quantum Theory of Energy: - E = nh E = energy of radiation n = positive integer H = Planck’s constant  = frequency - Planck’s constant = 6.626 x 10 -34Js - Quantized: occurs in fixed quantities, because each atom emits only certain quantities of energy - Quantum: fixed quantity. Equal to h. E = E = nh atom emitted (or absorbed radiation) (When n = 1… [E = h]) Chapter 7, section 2: Line Spectrum- a series of separated lines of different colors representing photons whose wavelengths are characteristic of an element Rydberg Equation: 2 2 - 1/ = R([1/n ]–1[1/n ]) 2 - n 1n a2d are positive integers - R is the Rydberg constant = 1.096776 x 10 m 7 -1  For the visible series, (n1= 2) and (n 2 3, 4, 5…)  Visible = ~400nm – 750nm Bohr Model: - The higher the energy level, the further away the orbit from the nucleus - An atom does not radiate energy while in one of its stationary states (an allowable energy level of an atom in which it doesn’t release or absorb energy). The atom does not change energy while the electron moves within an orbit - E photon= E atom= Efinal Einitial  Quantum # = n (is a positive integer associated with the radius of an electron orbit, which is directly related to the electron’s energy: (the lower the n value, the smaller the radius, and the lower the energy level)  Ground State  n = 1 (when the electron is in the first orbit it is closest to the nucleus)  Excited State  If the electron is in any orbit further away from the nucleus, the atom is in an excited state. - (2 orbit (first excited state)… n = 2, 3 orbit (second excited state)… n = 3…)  Absorption  if an H atom absorbs a photon whose energy equals the difference between lower and higher energy levels, the electron moves to the outer (higher energy) orbit  Emission  if an H atom in a higher energy level (farther orbit) returns to a lower energy level (closer orbit), the atom emits a photon whose energy equals the difference between the two levels Calculating a single energy level: -18 2 2 E = -2.178x10 J (Z / n ) *where Z is the charge of the nucleus*  For an H atom in ground state... -18 2 2 -18 E = -2.178x10 J (1 / 1 ) = -2.18x10 J Finding the difference in energy between two levels: -18 2 2 E = -2.178x10 J ([1/ n f]– [1/n ]i - When the atom emits energy the e moves closer to the nucleus (n final n initial So the atom’s final energy is a large negative number, and the E = negative - - When the atom absorbs energy the e moves away from the nucleus (n final initial So the atom’s final energy is a small negative number, and the E = positive Finding the energy needed to ionize the H atom: H (g) +(g)+ e- - We substitute n final  and n initial1 E = -2.178x10 -18J ([1/ n2f]– [1/n ]i = 2.18x10- J18 - Energy must be absorbed to remove the electron from the nucleus, so E is + - The ionization energy of hydrogen is the energy required to form 1 mol of gaseous H+ ion from 1 mol of gaseous H atoms. Thus, for 1 mol of H atoms: E = (2.18x10 -18J/atom)(6.022x10 atoms/mol)(1kJ/10 J) = 1.31x10 kJ/mol 3 Finding the Wavelength of a Spectral Line: - Once we know E from the equation above, we can find the wavelengths of the spectral lines of the H atom by combining the relation between frequency and wavelength E = h = hc/ or  = hc/E Spectrometry in Chemical Analysis: Emissions Spectrum (Such as the H atom line spectrum) occurs when atoms in an excited state emit photons as they return to a lower energy state. Flame Test Place a granule of an ionic compound or a drop of its solution in a flame Absorption Spectrum produced when atoms absorb photons of certain wavelengths and become excited. Chemical Formula: - In an ionic compound… name the cation first and then the anion - The anion (non-metal) will gain the suffix –ide - Acids: (anions) BINARY ACID (when hydrogen combines with an anion that has an –ide suffix) o Add a prefix hydro- o The root of the nonmetal o Add a suffix –ic o Finish with –acid - Acids: (anions) OXOACID o Add a prefix –hypo or –per o Root o Add a suffix –ic or –ous (ate  ic … ite  ous) o Finish with –acid - Binary Covalent Compounds: (Combination of two non-metals) o The element with the lower group # in the periodic table comes first o The second element will have the higher group #, and will have a suffix added to it (-ide) o If both elements are in the same group, the one with the higher period number is named first o When there is more than 1 of each element, they will have a Greek prefix added, stating how many there are (eg. di, tri, tetra…)  Molecular Formula = element symbols and numbers to give the actual number of atoms in each element of the compound. (H O,2HCl, H S2 ) 4  Structural Formula = shows the relative placement and connections of atoms in the molecule. (H:O:H, H–O–H) CHAPTER 3: section 3 Writing and Balancing Chemical Equations: - Reactants  Products - In a combustion reaction, balance by using CHO (C’s first, H’s second, O’s last)  Amphoteric – does not dissolve in water, but does dissolve in either acids or bases CHAPTER 1: section 1 Properties of Matter:  Properties- the characteristics that give each substance its unique identity - Physical Properties  Characteristics a substance shows by itself, without changing into or interacting with another substance  Include: melting point, conductivity, and density  A physical change occurs when a substance alters its physical properties, not its composition. (EG. ice melting) o Same substance before and after the change - Chemical Properties  Characteristics a substance shows as it changes into or interacts with another substance(s).  Include: flammability, corrosiveness, and reactivity with acids.  A chemical change occurs when a substance is converted into a difference substance o EG) the breakdown of water into hydrogen and oxygen when you run an electrical current through it  Three states of matter: 1. Solid – fixed shape, does not conform to containers 2. Liquid – varying shape, conforms to containers, does not fill containers 3. Gas – varying shape, conforms to containers, fills containers Importance of Energy: - Energy is often defined as the ability to do work - The total energy of an object includes its Kinetic Energy and its Potential Energy. o Potential Energy- the energy due to the position of the object relative to other objects o Kinetic Energy- the energy due to the motion of the object Rules: 1. Energy is converted from one form to another, never destroyed or created 2. Situations of lower energy are more stable, and therefore favored, over higher energy situations (less stable) CHAPTER 4: section 5 - Oxidation= the loss of electrons (more+ ) - Reduction= the gain of electrons (more –)  The oxidizing agent is the species that causes the loss of electrons  The reducing agent is the species that causes the gain of electrons  The OXIDATION NUMBER is what allows us to tell which atom lost and which atom gained Chapter 18: section 4 The Copper Cycle: 1. Copper reacts with nitric acid to form copper (II) nitrate, dinitrogen oxide and water Cu + 4HNO  Cu(NO ) + 2N O + 2H O 3 3 2 2 2  Heat given off  Brown smoke forms  A light blue liquid is produced 2. Copper nitrate reacts with sodium hydroxide to make copper hydroxide and sodium nitrate Cu(NO )3 2NaOH  Cu(OH) + NaNO2 3  Dark blue precipitate forms 3. Copper (II) hydroxide reacts with heat to form copper (II) oxide and water Cu(OH) +2heat  CuO + H O 2  The solution turns black - Next step is to remove impurities by allowing the black solid to settle and then washing it with wate
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