Basic Theory
Describe both homogeneous and heterogeneous mixtures.
Homogeneous: Uniformly distributed composition.
Heterogeneous: Not uniformly distributed composition.
The label on a box of cereal gives the mass of cereal in two units: 978 grams and 34.5 oz. Use this information to find a conversion factor between the English and metric units.
28.35 g/oz.
Describe: Protons, Neutrons, and Electrons.
Protons: Positively charged particles inside a nucleus. The number of protons is the sole deciding factor in which element an atom is.
Neutrons: They have no charge. They decide what isotope a certain case of an element is.
Electrons: Negatively charged particles in the "cloud" around a nucleus. Much less massive compared to protons and neutrons and are less bound to a certain atom.
Draw a diagram of the Mass-Mole-Particle conversion chart.
m/MM #Particles/NA
---> <---
Mass Mole Particle
<--- --->
m*MM #Particles*NA
Describe the three types of chemical formulas.
Molecular: The elements and their actual quantities with which they appear in a compound.
Empirical: The elements and their quantities divided by the least common denominator.
Structural: A physical model of the way the elements are formatted in reality.
What is the difference between crystalline and amorphous solids?
Crystalline: Have a consistent repeating order/structure in the arrangement of their molecules.
Amorphous: No repeating structure or pattern.
On a recent trip, Jan traveled 260 miles using 8 gallons of gas. What was the car’s miles per gallon for this trip? Kilometres per litre?
13.8 km/litre
What is Avogadro's number? What does it represent?
N = 6.022 * 10^23 unit: 1/mole
It represents 6.022 * 10^23 "things" per one mole. For our uses "things" are generally particles. Since there are an absurdly large number of particles in everyday items we use moles as a way of grouping them into nicer more easily internalizable numbers.
How many neutrons does an isotope of Fe-57 have?
31 neutrons
Describe what makes an ion polyatomic v.s. monatomic.
Monatomic ion: An ion that has only one element. Its charge comes from it not having filled its valence electron shell.
Polyatomic ion: An ion that consists of several elements that are covalently bonded. They are bonded very strongly together and are generally not separated during chemical reactions. Together they have a net charge.
What is the density equation? Give the standard units for all parts of the equation as well.
d = m/v
Units:
density has grams/(cm^3) or g/ml
mass has grams
volume has cm^3 or ml
Soccer is played with a round ball having a circumference between 27 and 28 inches and a mass between 14 and 16 oz. What are these specifications in cm and g?
1 inch = 2.54 cm
1 gram = 0.03527 oz
69 cm to 71 cm
4.0e2 g to 450 g
Describe both cations and anions.
Cations: ions with a positive charge.
Anions: ions with a negative charge.
How many electrons does Zn2- have?
32 electrons
Give the common prefixes up to ten for molecular compounds.
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
State the significant figure rules for both multiplication/division and for addition and subtraction.
Addition/Subtraction: The result of the operation has to have the same amount of significant figures after the decimal as the element with the least amount of sig figs after the decimal place.
Multiplication/Division: The result of the operation has to have the same amount of total significant figures as the element with the least amount of total significant figures.
You are buying carpet to cover a room that measures 38 ft by 40 ft. The carpet costs $18 per square yard. How much will the carpet cost?
3 ft = 1 yd
$3040
What is molar mass and how can you find it?
Bromine has two isotopes, 79-Br and 81-Br, whose masses (78.9183 and 80.9163 amu). 79-Br has an abundance of 50.69%. Calculate the average atomic mass of Br.
79.90 amu
When oxyanions become oxyacids their suffix changes. Fill in the blanks:
ate -->
ite -->
ate --> ic
ite --> ous
Describe the difference between the law of multiple proportions and the law of definite proportions.
The law of multiple proportions: elements can combine in many, many different ratios and structures to create different compounds.
The law of definite proportions: for any given compound there is only one ratio of specific elements in a specific structure that may make it.
An average human heart beats 60.0 times per minute. If the average person lives to the age of 86, how many times does the average heart beat in a lifetime?
2.7 * 10^9 beats
Describe the three types of radiation we discussed in class (gamma, alpha, and beta). Also, rank them in terms of severity.
Alpha: A discharge from an unstable atom. The discharge contains two protons and two neutrons (a helium atom).
Beta: An electron or positron that is emitted during beta decay. (when a proton turns into a neutron and vice versa.)
Gamma: A type of electromagnetic wave that can be generated from a number of processes such as radioactive decay, nuclear reactions, and certain types of interactions in astrophysics.
Lowest to Highest: Alpha --> Beta --> Gamma
The average mass of an Mg atom is 24.31 amu. A sample of magnesium is found to contain 78.70% of 24-Mg atoms (mass 23.98 amu), 10.13% of 25-Mg atoms (mass 24.99 amu), and an unknown Mg isotope. Calculate the percent abundance and the weight of the missing isotope.
26.02 amu and 11.17%
What is the empirical formula for a compound containing 38.8% carbon, 16.2% hydrogen, and 45.1% nitrogen?
CH5N