Lab Midterm (Labs 1-4)

Lab 1: Intro to Colorimetry, Dimensional Analysis Lab 2: Quantitative Colorimetry & Biuret Test (Concentration & Dilution) Lab 3: Molecular Models & Functional Groups Lab 4: Permeability (Diffusion & Dialysis)

What is a spectrophotometer?

an instrument that passes a wavelength of electromagnetic radiation through a solution and measures the amount of the radiation that the solution absorbs (doesn’t let thru) or transmits (lets thru)

What is the range of the electromagnetic spectrum and their wavelengths from most damaging to least?

gamma ray, x-ray, ultraviolet, visible light (380nm-780nm), infrared, microwaves, radio

In lab 1 (colorimetry intro), which spectrophotometer is used?

visible light/colorimeter (range: violet to red)

What is colorimetry/visible spectrophotometry?

a procedure in which a colorimeter is used to analyze the composition of solutions

What is a sunburn the result of cellularly?

the result of skin cell molecules absorbing the UV radiation from the sun

What is the difference between quantitative and qualitative properties?

quantitative depends on the amount of something and qualitative depends on the kind of something

What is transmittance?

relationship where the more concentration the solution, the more light that is absorbed and not allowed thru

What is absorbance (A)?

the relative amount of light of a given wavelength that is absorbed by a solution

What is percent transmittance (%T)?

the fraction of light that enters and passes thru the solution w/o being absorbed

Why calibrate the instrument before absorbing the light of the actual substances?

have to “correct” for light absorption of the one molecule by subtracting everything else (container, solvent, other color-producing reagents)

In lab 1 (colorimetry intro), what is the molecule of absorption interest?

riboflavin: yellow, water-soluble vitamin

What is a blank?

used to calibrate an instrument

In lab 1 (colorimetry intro), what is the blank before recording riboflavin wavelengths?

water

How are absorbance (A) and percent transmittance (%T) related?

reciprocally proportional; A=log(1/T)

What is riboflavin’s maximum wavelength?

~445nm

How many peaks does riboflavin have? At which wavelengths?

2; ~370nm & ~445nm

Convert mega- (M) to base unit.

1 M = 10^6 base

Convert kilo- (k) to base unit.

1 k = 10³ base

Convert hecto/a- (h) to base unit.

1 h = 10² base

Convert deca- (da) to base unit.

1 da = 10

Convert deci- (d) to base unit.

10^-1 d (0.1 d) = 1 base

Convert centi- (c) to base unit.

1 c = 10^-2 base (0.01 base)

Convert milli- (m) to base unit.

1 m = 10^-3 base (0.001 base)

Convert micro- (µ) to base unit.

1 µ = 10^-6 base (0.000001 base)

Convert nano- (n) to base unit.

1 n = 10^-9 base (0.000000001 base)

Convert pico- (p) to base unit.

1 p = 10^-12 base (0.000000000001 base)

What is the conversion of cups to fluid ounces (fl. oz.)?

1 cup = 8 fl. oz.

What is the conversion of pints (pt.) to cups?

1 pt. = 2 cups

What is the conversion of quarts (qt.) to pints (pt.)?

1 qt. = 2 pt.

What is the conversion of gallons (gal) to quarts (qt.)?

1 gal = 4 qt.

What is the conversion of feet (ft.) to inches (in.)?

1 ft. = 12 in.

What is the conversion of feet (ft.) to yards (yd.)?

3 ft. = 1 yd.

What is the conversion of miles (mi.) to feet (ft.)?

1 mi. = 5280 ft.

What is the conversion of pounds (lbs.) to ounces (oz.)?

1 lb. = 16 oz.

What is the conversion of tons to pounds (lbs.)?

1 ton = 2000 lbs.

What is the conversion of liters (L) to quarts (qt.)?

1 L = 1.06 qt.

What is the conversion of meters (m) to inches (in.)?

1 m = 39.4 in

What is the conversion of pounds (lbs.) to grams (g)?

1 lb. = 453.6 g

In lab 2 (biuret & dilution), what is the molecule of interest?

BSA, bovine serum albumin: an abundant protein in cow blood

What is biuret? Draw its molecular structure.

small collection of proteins in blood; produces violet color when reacted with CuSO4 and NaOH in aq solutions

What is the Beer-Lambert law/standard curve?

A=ecl; there exists a concentration range within which there is a direct, linear relationship between solute concentration and absorbance

In lab 2 (biuret & dilution), what is the blank solution for calibration?

KCl and biuret reagent, no albumin since that’s the molecule of interest

How do you title graphs of data?

y-axis (dependent variable) vs. x-axis item (independent variable)

In lab 2 (biuret & dilution), what is the dependent variable (y-axis) and the independent variable (x-axis)?

dependent variable: absorbance

independent variable: solute concentration

Convert 49.5 kg to mg.

49500000 mg = 4.95×10^7 mg

If you dilute 175 mL of a 1.6 M solution of sucrose solution to 1.0 L, determine the new concentration.

C1V1=C2V2

1.0 L —> 1000 mL

(175 mL)(1.6 M)=C2(1000 mL)

C2=0.28 M

If you have 1 mL of a 0.5 M HCl solution and it is diluted by adding 9 mL of H2O, what is the new concentration of your solution expressed as molarity?

C1V2=C2V2

(1 mL)(0.5 M)=C2(1+9 mL)

C2=0.05 M

What is the chemical formula and molecular geometry of methane?

CH4, tetrahedral

What is the chemical formula of ethane?

C2H6

What is diffusion?

the movement of particles (ions or molecules) from areas of high concentration to low concentration

What is passive movement?

diffusion of particles through a selectively permeable membrane

What is dialysis?

type of passive movement with only one solute allowed to pass; selective permeable membrane separate two solutes in the same solution

What is osmosis?

type of passive movement with only water allowed to pass

What are hypertonic solutions?

solutions with much more water absorbed

What are hypotonic solutions?

solutions with much less water; shriveled

What are isotonic solutions?

solutions with a balanced amount of water

Osmotic pressure is a _____ property.

colligative; depends on amount of solute, not the type of solute

_____ bonds hold together the many amino acids of protein.

Peptide

What are isomers?

molecules that have the same chemical formula but different structures/arrangement

There is no _____ _____ at a double bond.

free rotation

What are biological molecules (BIOM)?

molecules that must contain carbon for it’s bonding properties; carbohydrates, fatty acids, fats (triglcerides, triglycerols), phospholipids, steroids, amino acids & proteins

What are alkanes?

made of only methyl function groups (-CH3); hydrophobic, flammable

What are alcohols?

contain hydroxyl functional group (-OH); 1-4 C = hydrophilic (water soluble) and larger alcohols with more methyl groups = hydrophobic

What determines solubility?

having an electronegative charge and h-bonding properties

What are functional groups?

chemical groups that affect molecular function of larger reactions; hydroxyl (OH), carbonyl (C=O), carboxyl (COOH), amine (NH3), methyl (CH3), keytone (end), aldehyde (middle)

What is the difference between cis and trans isomer structures?

cis —> \=/ and trans —> \=\