AP Chemistry Unit 3.7-13

tf even is light

Solvent

The substance that dissolves another

Solute

The substance that is dissolved by another

In a mixture, there is usually __________ solvent than solute

more

__________ is the universal solvent

Water

Molarity equation

(Moles of solute)/(liters of solution)L

Larger molarity = _________ concentration

larger

A solution in which a substance is dissolved completely in water is known as an _______ solution

aqueous

How do you perform a dilution?

Add distilled water to s solution

What formula can you use to figure out molarity in a dilution?

M₁V₁ = M₂V₂

Why do you rinse the weighing paper when adding solute to a solvent?

Solute may stick to the weighing paper/container

What kind of flask is used for a dilution?

Volumetric flask

The components of a liquid solution cannot be separated by…

filtration

What are the two methods in which a liquid solution can be separated?

Chromatography, distillation

Chromotography

Separates chemical species by taking advantage of the differential strength of the IMFs between and among the components of the solution/mobile phase and with the surface components of the stationary phase

Chromatography can help infer the relative _____________ of components in a mixture

polarities

Stationary phase

A solid that provides support for the chromatography experiment, but does not move → can be piece of paper, piece of metal/glass coated with a porous solid, or a glass column filled with a porous solid

Mobile phase

A liquid or gas that moves, carrying the components of the mixture over or through the stationary phase

In a chromatography experiment, if Component X travels farther away from a nonpolar solvent/mobile phase than Component Y, Component X is more ___________

nonpolar

Substances with ____________ IMFs tend to be more soluble in one another; in other words, _________ dissolves _________

similar; like dissolves like

Solvent front

In a chromatography experiment → the mark on the paper that indicates how far the solvent has moved up the paper

Retention factor (R_f) formula

(Distance traveled by one component)/(distance traveled by the solvent)

The larger the R_f value is the farther _____ the paper he component of the mixture has traveled relative to the solvent front

up

Distillation

Separates chemical species by taking advantage of the differential strength of IMFs between and among the components and the effects these interactions have on the vapor pressures of the components in the mixture; separates components of a mixture that have different boiling points

In a distillation, the mixture is heated gently until the component with the ________ boiling point begins to boil. The vapor rises up through the glassware, and reaches the ____________, which is the portion of the apparatus that is surrounded by cool _____________. The vapor condenses into a liquid and is collected in a separate container, The liquid that is produced in a distillation experiment is known as the _______________. The component of the mixture that appears first in that is the one with the _____________ boiling point.

lowest, condenser, water, distillate, lowest

Ionic compounds MUST dissolve in _________

water

Polar and nonpolar only refers to _____________ molecules

nonmetal

What are the three types of electromagnetic radiation (EMR)?

Microwave, infrared, ultraviolet

Microwave radiation causes a molecule to…

rotate

Infrared radiation (IR) causes the bonds in a molecule to…

vibrate

Visible/ultraviolent (UV) radiation causes electrons in the molecule to…

move up to higher energy levels

Wavelength (𝜆)

Length of wave (period) in meters/nanometers

Frequency (v)

Number of cycles passing a point in a given time (cycles per second → hz)

Speed (c)

The speed of light, at which all electromagnetic radiation travels at

How do wavelength, frequency, and speed relate?

c = 𝜆v

What is represented by h?

Planck’s constant

How can you find the energy of a photon?

E = hv

Photoelectric effect

When light shines on the surface of a metal, electrons can be ejected from the surface (and thus, E = hv)

If E = hv, and c = 𝜆v, how can you combine the equations for simplicity?

E = (hc)/𝜆

Amount of energy needed to remove an electron is measured by…

threshold frequency (v₀)

Ionizing energy

Any wavelength/energy that causes the loss of electrons

Which color of light can’t remove electrons from any element?

Red

Colors result from _______________ (______________) between energy levels in atoms

quantum leaps, electron jumps

Is this unit real

no

Beer-Lamber law relates the ____________ of light to three variables according to the equation…

absorption; A = εbc

Molar absorptivity (ε)

Describes how intensely a chemical species absorbs light of a specific wavelength (L / mol cm)

The pathlength (b) and concentration (c) are proportional to the number of __________________________ in the light path

light-absorbing particles

In most experiments, the pathlength and wavelength and held ___________

constant

What value do we assume the pathlength (b) is, unless told otherwise?

1

Color absorbed is the ___________ of the color observed

opposite

When a substance absorbs light, electrons in the ground state become _____________ and move to __________ energy levels

excited, higher

A ______________ or _________________ is an instrument that consists of a light source and a diffraction grating that separates the light into different ____________. The light passes through a ____________, which is a small test tube or square container used to hold the sample that is being analyzed. After the light passes through the sample, a detector measures how much ____________ passes through the sample. Most spectrophotometers are designed to measure absorbance in the ___________ or ____________ region of the electromagnetic spectrum.

spectrophotometer, colorimeter; wavelengths; cuvette; light; visible, ultraviolet

Incident light

The original beam of light in a spectroscopy experiment

Transmittance (T)

Ratio of amount of light transmitted to the incident light

Transmittance formula

T = I₁ / I₀
OR
T = (light out)/(light in)

How does absorbance (A) relate to transmittance (T)?

A = -log(T)

As concentration increases, absorbance…

increases

Molarity is a way of expressing…

concentration (mol/L)

What is a calibration curve made from?

Constructed from absorbances of solutions with known calculations, using a line of best fit to determine concentration of an unknown solution based upon its measured absorbance

What does the slope equal on a calibration curve (given y = mx + b)?

The molar absorptivity (ε)

Will there be more or less absorbance if a cuvette has finger prints on it?

More

Why is it important to wipe a cuvette clean before placing it into a spectrophotometer?

It may have fingerprints on it, which would cause absorbance to be higher than it should be

According to Beer’s Law, absorbance should increase ___________ with concentration

linearly

Which colors are opposites of red, blue, and yellow?

Red → green, blue → orange, yellow → purple

A substance that can create hydrogen bonds tends to be ________ soluble in water

more

1 Nanometer = _________ meters

1 × 10^-9

1 Meter = ________ nanometers

1 × 10⁹

As wavelength (𝜆) lets larger, energy (E) gets __________

smaller

When an electron jumps down an energy level, a photon is ____________, and thus the energy of the atom _____________

emitted, decreases

To calculate the minimum amount of energy required to ionize an atom, divide its ________________ by _______________

first ionization energy, Avogadro’s number