Chemistry Flashcards
Safety rules in the Lab
- no eating or drinking in the lab
- always use safety goggles, lab coat, closed toed shoes, gloves
- Volatile or dangerous chemicals should be handled in the hood, and a far mask or respirator may be needed
- all labs should have a eyewash station and shower station
- fire extinguishers
- more than one exit
- disposal of lab waste should be done safely and appropriately and containers should be set up for different types of waste
Accuracy
refers to a measurement giving the actual value for the sample with a limited deviation
EX: correctly determining the weight of a sample to be 1 gram plus or minus .001 gram is accurate
Precision
is the repeatability of a set of measurements on the sample
EX: measuring the same 1 gram sample three times in a row and finding values of 1.001 g, 1.00 g and 1.001 g-these are precise but not accurate
Laboratory Glassware
applies to a variety of vessel not all of which are actually made of glass.
Why is glassware usually preferred by chemists?
strength, inertness, transperancy, and heat resistance
How is plastic preferred over glass in some instances?
- plastic is better when using a chemical that can interact with a glass surface
- is also lightweight and difficult to break
Non-Calibrate Glassware
- these items are simply used for containing, mixing, and reacting without specifically measuring the experimental materials.
- include test tubes, beakers, Erlenmeyer falsks, round-bottomed flasks, transfer pippets, petri dishes, watch glasses, bottles, jars and vials
- these have volume markings but they are approximate and should not be used for actual measurements
Test tubes
relatively small and allow a large number of samples to be arrayed in a rack for easy pocessing
-used for routing mixing and reaction tasks
Beakers
wide mouthed cylinders with a lip to allow for pouring
-have flat bottoms so they can stand on their own
Erlenmeyer Flasks
are tapered and therefore minimize accidental spills
- the neck allows it to be clamped in place either on the laboratory bench or above it on a stand
- some have a side hose barb to allow connection to a vacuum apparatus
- can be sealed with a rubber, cork, or ground glass like stoppers
- have flat bottoms so they can stand on their own
Round Bottom Flasks
are used for reaction, heating, or vacuum applications
- spherical shape and wall thickness of the flask provides extra strength and fit into a heating mantle
- the narrow neck allows the flask to be clamped into place.
- the top of the neck often has a ground glass joint to allow a stopper or glass tube to be connected to the flask
Retort
a round vacuum flask with a long neck that extends to the side.
-used for distillation and must be placed on a ring stand or heating mantle
Extraction Flask
also known as a separatory funnel
- teardrop-shaped flask with a ground glass stopper at the top and a stopcock at the bottom
- Two different solvents are mixed by shaking the flask and are then allowed to separate: the lower level is removed by draining the stopcock
- the flask cannot stand on its own so it typically is placed in a ring stand to keep vertical
Funnel
- used for transferring liquids
- allows pouring from one vessel to another with minimal spillage
Transfer pipets
are often made of plastic and have an integral bulb at the top
-often used when small amounts need to be transferred
Pasteur Pipets
are made of glass with a long tapered tip and require a separate rubber pipet bulb
-often used when small amounts need to be transferred
Bottles
containers with narrow openings generally used to store reagents or samples
what are small bottles called?
Vials
Jars
Cylindrical containers with wide opening that may be sealed
Bell Jars
are used to contain vacuums
Watch Glasses
also known as evaporation dishes
-shallow glass plates used as evaporation surfaces or to cover beakers
Petri dishes
are flat dishes with vertical sides used to culture living things
Callibrate Glassware
should be used for any laboratory measurement that requires accuracy and precision
- manufactured to provide exact volumes at a given temp, usually 25 C
- Available in a broad range of sizes from millimeters to several liters
Graduated Cylinder
tall, narrow tube with volume markings increasing from bottom to top and a lip at the top for pouring
- a liquid is poured into the graduated cylinder to the approximate desired level and then carefully added to or removed form the cylinder to reach the exact volume required.
- The fluid is then transferred to another vessel
- Have wide bases and often have protective plastic rings around the top of the cylinder to protect them from spilling and breaking
Buret
- used to deliver a exact amount of liquid
- is a long tube that is clamped in place vertically with a stopcock at the bottom.
- The amount delivered is determined by the difference between the starting volume and the final volume in the buret.
- especially useful when liquids are to be dispensed slowly or drop wise
- are used to make solutions and to perform titrations
Graduated Pipete
- hand-held and controlled by a pipet bulb that maintains a slight vacuum at the top of the pipet.
- can deliver a variable amount of liquid, as either all of the fluid is dispensed or the top and start volumes are measured
Volumetric pipetts
have a large bulge in the middle of the tube and deliver a single established volume of liquid with great accuracy and precision
Volumetric Flask
used to make solutions that require a specific volume of liquid such as molar solutions
- the components are added to the flask with less solvent than is required The contents are mixed and then a final amount of solvent is added to read the volume marking on the neck of the flask
- have flattened bottoms so that they can stand and narrow necks so that the vole mark can easily be read
pH meter
- consists of a glass probe and an electronic meter
- it determines the acidity or basicity of a solution by comparing the voltage produced by the solution compared to the voltage of a known standard solution and uses the difference in voltage between them to calculate the pH.
- The glass probe is firth calibrated then rinsed, dried, and quickly immersed in the solution to be measured
- Calibration is done at an appropriate range of pH values to match the sample to be measuered
Litmus Paper
can be used to quickly determine pH
- less accurate than a pH meter
- tradition litmus paper is red under acidic conditions (below pH4.5), blue under basic conditions (above 8.3) and purple at neutral pH
-Modern Litmus paper is available that is calibrated with different colors according to the pH range, typically with a different color at each integer pH
Standard Laboratory Balances
also called top-loading blanches
-are used when weights are in the milligram range and require accuracy to within plus or minus .5 mg.
Analytical balances
used for much more sensitive weighing application, with accuracy to plus or minus .01 mg
-have glass sides and sliding doors to protect against sleigh movements due to drafts and must be used with particular care
Atom
- is the basic building block of matter
- represents the smallest unit of a chemical element
- is composed of subatomic particles: protons, neutrons, and electrons
What forms the nucleus of an atom
the protons and neutrons
Isotopes
atoms of the same element with different masses due to different numbers of neutrons
-have different number of neutrons but the same number of protons
-
Proton
- carry a single positive charge
- has a mass of one UNIFIED ATOMIC MASS UNIT (amu or u) which is equivalent to one DALTON (Da)
Atomic Number (Z)
is equal to the number of protons found in an atom of that element
Neutrons
- carry no charge
- have a mass slightly larger than that of protons, so they can still be considered to have a mass of approximately 1 amu
Electrons
-carry a negative charge
-has a very small mass compared to a proton or neutron
-
Valence Electrons
are the electrons in the electron shell farthest from the nucleus
-the farther the valence electrons are from the nucleus, the weaker the attractive force of the positively charged nucleus and the more likely the valence electrons are to be influenced by other atoms
Mass number
is equal to the total number of nucleons (protons and neutrons)
molecular weight
is the weight in grams per one mole of a given element
Standard Atomic Weight
is a weighted average of all the isotopes of an element, which accounts for the relative abundance of the various isotopes
electron configuration
- the first number denotes the principal energy level
- the letter represents the subshell
- the exponent represents the number of electrons in that subshell
-ml and ms are not indicated in electron configuration
Aufbau principle
subshells are filled from lowest to highest energy, and each subshell will fill completely before electrons begin to enter the next one
- the (n+l) is used to rank subshells by increasing energy
- if two subshells possess the same (n+l) value, the subshell with the lower n value has a lower energy and it will come first
Hund’s Rule
within a given subshell, orbitals are filled such that there a maximum number of half filled orbitals with the same spin.
-if there are extra electrons left you fill in the rest
Why do electrons prefer empty orbitals vs. half filled orbitals
-electrons prefer empty orbitals to half filled ones because a paring energy must be overcome for two electrons carrying repulsive negative charges to exist in the same orbital
Paramagnetic
-when the presence of unpaired electrons affects the chemical and magnetic properties of an atom or molecule. IF the material has unpaired electrons, a magnetic file will align the pains of these electrons and weakly attract the atom to the field
Diamagnetic
materials that have no unpaired electrons and are slightly repelled by a magnetic field
Periodic Law
chemical properties of the elements are dependent upon their atomic numbers
