midterm (kms) Flashcards
if a small fire breaks out on your bench you should
either invert a beaker over it to deprive it of O2 or call for the fire blanket
wash (“squirt”) bottles should be filled ‘only’ with
deionized water
you can’t use a beaker to
measure the exact amount of something
1 cubed cm of lead has a mass of 11.34 g. This statement represents lead’s
density
How many millimeters in .62 cm
6.2 mm
convert 300 decaliters to centiliters
300,000 cL
find the sum: 2.17+4.32+401.278+21.821
429.59
u measured the length of an index card to be 7.3 cm. it’s supposed to be 7.5 cm. what’s the percent error?
2.7%
When doing the calculation 25.1 x 453.2, how should you report your answer?
11,400
round 90,221 to 4 significant digits
90,220
what is 24.57+5.678+5.3?
35.5
what’s 0.0012/5.9?
0.00020
what’s 59.34 x 5?
300
what’s 8.895-6.22?
2.68
what’s the specific heat of a substance if 1560 cal is needed to raise the temp of a 312 g sample by 15 degrees Celsius/
0.33 cal/g C
how many kilojoules are equal to 3254 calories?
13.61 kJ
how many kilocalories of heat are required to raise the temperature of 225 g of Al (C of Al is 0.21 cal/g C) from 20 Celsius to 100 Celsius?
3.8 cal
the amount of heat transferred from an object depends on all the following except:
a. the specific heat of the object
b. the change in temperature the object undergoes
c. the initial temperature of the object
d. the mass of the object
c
is a calorie smaller than, larger than, or the same size as a joule?
larger than
in an exothermic reaction, the energy stored in the chemical bonds of the reactants is
greater than the energy stored in the bonds of the product
Boyle’s law states that
the volume of a gas varies inversely with pressure
Charles’s law states that
the volume of a gas is directly proportional to its temperature in Kelvin
If a sealed syringe is plunged into cold water, in which direction will the syringe piston slide?
in
A sample of gas occupies 17 mL at -112 C. What volume does the sample occupy at 70 C?
36 mL-remember to convert to Kelvin!
At high pressures, how does the volume of “real gas” particles compare with the volume of “idea gas” particles under the same conditions?
it’s much greater
gases are characterized by
no intermolecular interactions present particles
Which statement about atmospheric pressure is false?
1. as air becomes thinner, its density decreases
2. air actually has weight
3. with an increase in altitude, atmospheric pressure increases as well
4. the colder the air, the lower the atmospheric pressure
3
pure substances made up of more than 1 element are called _______
compounds
boiling water is classified as a(n) (exothermic/endothermic/neither) process
endothermic
in order to separate a mixture of salt and water, you can use
distillation
to break bonds, you need to ____ energy
add
density is a (qualitative/quantitative), (intensive/extensive) property
quantitative, intensive
btw when a question like “how long did a substance take to freeze” is asked it’s asking how long the FREEZING process took. it’s just isolating the freezing. it’s not from te beginning of the curve
what element in the fourth period has 2 valence electrons?
Ca (calcium)
chemical bonds can be produced by any of the following processes except:
a. splitting electrons
b. gaining electron
c. losing electrons
d. sharing electrons
a
look for notes regarding how to tell the melting point/polarity/etc of a compound from its name
What’s the symbol for the ion formed when zinc (Zn) loses its valence electrons?
Zn^-2
Aluminum hydroxide has the formula:
Al (OH)3
the chemical name of IBr is
iodine monobromide
An unknown element is found to have 3 naturally occurring isotopes with atomic masses and relative abundances of
41 (1%) 39 (2%) 40 (97%)
Which of the following is the unknown element?
a. Ar
b. K
c. Cl
d. Ca
Ar (a)
How many grams are in 5.57x10^23 atoms of copper?
58.8g
find the empirical formula of a compound with a percentage composition of 52.3% C, 13% H, and 34.7% O
a. CH3O
b. C2H6O
c. C2H6O2
d. C4H12O2
b
What characterizes solids?
- very high density
- particles vibrate around a fixed position relative to each other
- particles are tightly packed together
- completely incompressible for most applications (unless you get a hydraulic press)
- definite shape and volume
- strong particle attraction
- forms crystals when particles are locked into a geometric shape
- very low kinetic energy
- has mass
what characterizes liquids?
- weak particle attraction
- particles are relatively close together
- virtually incompressible for most applications
- intermolecular forces cause surface tension and capillary action
- particles slide past each other
- definite volume, no definite shape
- low to high kinetic energy
- can flow
- has mass
what characterizes gases?
-condense
-highly compressible
-virtually no particle attraction
-mostly empty space
-particles bounce off of each other
-very compressible
-expands by diffusion to completely fill chamber
-particles are very far apart
-no definite shape or volume
-very low density
-very high kinetic energy
-has mass
-can flow
-ideal behavior at low pressure, high temperature
endothermic
when system gets warmer and surroundings get colder (ex. boiling)
exothermic
when systems get colder and surroundings get warmer (ex. freezing)
general lab rules
- don’t pipette by mouth
- don’t assume that any unknown chemical is safe
- don’t step over danger lasers
- don’t cover up first aid
When should the fire blanket be used?
for fires on you/bench
kinetic molecular theory (KMT)
- particles of matter are in constant, random motion
- avg speed of particles increases w temp
- macroscopic properties of matter dependent on motion at particle level
- interactions among particles, particularly in liquids and solids, determine physical properties of matter
What is the difference between temperature and heat?
- temperature: a measure of the average kinetic energy of the particles (kinetic energy has to do with speed, so temperature only depends on speed)
- heat: a type of energy that can be transferred between 2 substances which have different temperatures (heat flows from warmer objects to cooler objects until thermal equilibrium is reached)
calorimetry
the measurement of heat change for chemical and physical processes
intensive property
a characteristic of a substance that depends on the type of matter present (ex. density, color, specific heat, capacity, melting point, boiling point)
thermal equilibrium
when energy flow between 2 substances stops because their temperatures are equal
difference between potential and kinetic energy
potential (ex. chemical, nuclear, mechanical) is stored energy while kinetic (ex. heat, light, sound) involves motion
What does potential energy do in a heating curve?
it decreases
What’s the equation for pressure?
force/area
kinetic molecular theory of gases (KMT)
- the volume of all the molecules of gas is negligible compared to the total volume of the container that holds the gas
- gases consist of big numbers of molecules/atoms that are in continuous, straight line motion
- no present intermolecular forces in between gases
- energy is transferred between molecules during collisions. the collisions are perfectly elastic, meaning the molecule’s total average kinetic energy stays the same
- increase in temp increases avg kinetic energy (this is true for any matter but whateva)
When do gases start behaving less ideal?
as they approach liquid phase (low temp, high pressure)
What are the pressure conversions?
1atm=760mmHg=760torr=101.3kPa=101,300Pa=14.7psi (pounds per square inch)
filtration
separating heterogeneous mixtures of solids and liquids based on differences in size or solubility
decanting
separates a liquid from atop a solid in a heterogeneous mixture
centrifugation
separates heterogeneous mixtures based on density differences by spinning a rotor around at several thousand times the force of gravity. denser substance settles to bottom
evaporation/distillation
- separates homogenous mixtures based on differences in boiling points
- when a solution is heated, the pure substance with the lower boiling point vaporizes first, leaving the other pure substance(s) behind
extensive
extensive properties depend on amount of matter (ex. volume, mass, energy)
what’s the difference between physical and chemical properties?
physical
- can be observed/measured without changing the identity of the substance
- physical properties describe the substance itself, mainly by using your 5 senses
- classified as qualitative/quantitative and intensive/extensive
- ex. color, odor, taste, hardness, density, texture, viscosity, state of matter, solubility, malleability, ductility, tensile strength, composition, specific heat, size, volume, surface tension, pH, magnetic, mass, length, width, height, weight, luster, color, shape, temperature, conductivity
chemical
- properties that can be observed/measured during/after a chemical change
- describes how the substance interacts with other substances to produce a new substance
- ex. combustibility, corrosive, oxidizer, reducer, tarnishes, reactivity, rotting, spoiling, decomposing, degrading, flammability, rusting
solution
- mixture with uniform composition
- no distinct parts or layers
- no Tyndall effect, filtering out, or settling
colloid
- mixture w medium sized particles
- doesn’t settle out
- has Tyndall effect
suspension
- largest sized particles
- can be filtered out
- will settle out
- has Tyndall effect
What is the difference between metals vs nonmetals vs metalloids?
metals
- hard solids with loosely held electrons
- good conductors of heat & electricity (they conduct electricity well because their electrons are more freely moving and floating)
- high melting and boiling points
- can form ionic compounds with nonmetals
- usually gray and shiny
nonmetals
- can form ionic compounds with metals (polyatomic
- dull, colorful/colorless substances with tightly held electrons
- low melting and boiling points
- bad conductors of heat and electricity
- 2 or more nonmetals can form covalent compounds (molecules)
metalloids
- chemical elements that have properties of metals and nonmetals
- so unoriginal tbh. pmo
What are the pieces of evidence of a chemical change?
- weird color change (ex. clear+clear=pink)
- formation of gas (bubbles)
- formation of solid (precipitate=insoluble solid)
- emission/absorption of energy (heat/light/sound)
- change in odor/taste
hydrogen bonding
where a H molecule is bonded to a F, O, or N molecule (d-d)
What is another way of expressing id-id forces? Gimme some info on that
- London dispersion forces (LDF)
- nonpolar bonds basically
- the bigger the size, the bigger the attraction
- occur for all substances w electrons but are the only force acting on nonpolar molecules
- results from random/induced elecron fluctuatings, which create tiny, temporary dipoles
What is another way of expressing id-d forces?
polar+nonpolar molecules
The stronger the IMF attraction, the (harder/easier) it is to separate molecules and evaporate
harder
The bigger a molecule, the (more/less) viscous it is.
more
The bigger a molecule, the (higher/lower) its boiling or melting point
higher
Polar substances tend to have (higher/lower) melting points
higher
Nonpolar substances tend to be (more/less) viscous
less
magnetism
some solids are magnetic (ex. iron) and can be easily separated from non-magnetic solids
chromatography
- separates a homogenous mixture
- mobility rates are based on difference in solubility/absorption
electrolysis
chemically separating water using polarity (ex. batteries where negative electrode had less bubbles and brownish tint and positive electrode had more bubles)
NO3 -1
nitrate
NO2 -1
nitrite
bisulfate
HSO4 -1
sulfate
SO4 -2
sulfite
SO3 -2
bicarbonate
HCO3 -1
carbonate
CO3 -2
phosphate
PO4 -3
chromate
CrO4 -2
dichromate
Cr2O7 -2
ionic bonds/compounds vs metallic bonds/compounds vs covalent bonds/compounds (definition and properties)
ionic
- formed when a metal gives up 1 or more electrons to a nonmetal resulting in charged cations and anions
- solid
- strong bond
- high melting and boiling points
- soluble in water
- dissociates in water
- conducts electricity
- oppositely charged ions in an ionic compound arrange themselves in a tightly packed, 3d structure called a crystal lattice
- brittle
- don’t conduct electricity when solid but conduct electricity when dissolved in H2O
- ionic substances can be shattered along cleavage lines
metallic
- occurs between 2 or more metal atoms
- not soluble in water
- valence electrons in a metallic bond are free-floating and are shared between the metal atoms (the so-called sea of electrons)
- malleable (they deform instead of breaking)
- ductile
covalent
- occurs between 2 or more nonmetal atoms
- electrons are shared
- liquids or gases
- weak bond
- don’t conduct electricity
- low melting and boiling points
- insoluble in water
- doesn’t dissociate in water
- doesn’t conduct electricity in water
ionic vs covalent
- occurs between metal atoms
- valence electrons in a metallic bond are free-floating and are shared between the metal atoms (the so-called sea of electrons)
octet rule
- atoms gain, lose, and share electrons to fill their valence shell with 8 electrons
group 16 on periodic table
chalcogens
gimme the 3-2-1 staircase
Al (+3)
Zn (+2)
Ag (+1)
Roman numerals indicate (+/-) charge
+
gimme the 10 prefixes for molecules
1-mono
2-di
3-tri
4-tetra
5-penta
6-hexa
7-hepta
8-octa
9-nona
10-dec a
What are the masses in amu of subatomic particles?
protons: 1 amu
neutrons: 1 amu
electrons: 1/1800 amu (essentially 0)
more stable isotopes are (more/less) abundant in nature than radioactive isotopes
more
What makes up a nuclear symbol?
mass number on northwest corner (protons+neutrons)
atomic number on southwest corner (protons)
average atomic mass
a measure of the weighted average mass of all the isotopes in a naturally occurring sample of the element (expressed in amu)
explain hyphen notation for something like boron-11 or boron-10
the number after the dash represents the atomic mass of that isotope
