Mrt - The 50 Worst

Front 1

Define the terms: atomic number, mass number and isotope.

Back 1

Atomic number: The number of protons in the atomic nuclei of a chemical element

Mass number: The total number of protons and neutrons (i.e. the number of nucleons) in an atomic nucleus of an atom

Isotope: Types of atoms that have the same number of protons but different number of neutrons in their nuclei

Front 2

Define the term of mole and give the value of Avogadro constant.

Back 2

1 mole is the amount of a chemical substance that contains as many elementary entities (atoms, molecules, ions, electrons or photons) as there are atoms in 12 g of carbon-12 isotope.

6.02×10^23 mol^−1

Front 3

Define the term of electronegativity and the direction of its change within the rows and columns of the periodic table of elements.

Back 3

Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons to itself.

It increases to the right in the rows and upwards in the columns of the periodic table.

Front 4

Characterize the σ bond. (Sigma bond)

Back 4

The σ bond is the strongest covalent bond due to the fact that the bonding electrons can be found in a rotationally symmetrical arrangement along the axis of the bond. Single covalent bonds are typically σ bonds.

Front 5

Characterize the π bond. (pi bond)

Back 5

The second and/or third bond of multiple covalent bonds is a so called π -bond. The bonding electrons can be found above+under and/or behind+in front of the axis of the bond. It is weaker than the σ bond.

Front 6

Give the hybrid state of the carbon atom and the bond angles around the carbon atom in ethane, ethene (ethylene) and ethyne (acetylene) molecules.

Back 6

Front 7

List the intermolecular chemical bonds in the order of increasing bond energy.

Back 7

1) van der Waals-interactions (hydrophobic interactions, London dispersion interactions)

2) Dipole-dipole interaction

3) Hydrogen bond

Front 8

Name the molecular criteria necessary for hydrogen bond formation. Name physical properties that may refer to the presence of hydrogen bonds.

Back 8

The donor of the H-bond must contain a polarized E-H bond (E=element, mostly N,O, F) whereas its acceptor must contain a free (nonbonding) electron pair. The presence of H-bonds can cause high melting point and boiling point (compared to the molecular weight) or good water solubility.

Front 9

How to calculate absolute temperature values (Kelvin scale) from or to the centigrade (Celsius scale)? Write an equation with explanation of the denotations.

Back 9

T = t + 273.15

where

T = absolute or thermodynamic temperature(given in Kelvin)

t = is the temperature in degree Celsius

Front 10

Write the equation of the ideal gas law with the explanation of the denotations.

Back 10

Front 11

Define the terms: mass percent, mass-per-volume percent and molarity

Back 11

Mass percent: x g solute / 100 g solution

Mass per volume percent: x g solute / 100 mL solution

Molarity: x mol solute / 1 L solution

Front 12

Define the term: colligative property. Name four colligative properties.

Back 12

Colligative properties are properties of substances that are assumed to depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the type of chemical species present.

Examples:

- lowering of vapour pressure

- elevation of boiling point

- depression of freezing point

- osmotic pressure

Front 13

Write the equation of the osmotic pressure law with the explanation of the denotations.

Back 13

Front 14

Define the terms: isotonic, hypotonic and hypertonic solution. Give the percentage andmolarity of the physiological saline.

Back 14

In isotonic solutions the osmotic pressure is equal to the intracellular osmotic pressure. Πsolution = Πcell

In a hypotonic solution: Πsolution < Πcell

In a hypertonic solution: Πsolution > Πcell

The concentration of the physiological saline: 0.9 % (= 9 g/L) or 154 mM NaCl

Front 15

Describe briefly the molecular level events taking place during hemodialysis.

Back 15

The blood of the patient is driven through a tube surrounded by a semipermeable dialyzing membrane, which allows the small molecules pass through but withholds the colloidal sized ones (like proteins, colloidal lipids, cells). The blood is dialysed against a dialyzing liquid,which is isotonic to blood and contains essential molecules (e.g. glucose) in the same concentration as blood.

Front 16

Classify the colloids by the states of the phases.

Back 16

Front 17

Define the terms: strong and weak electrolytes and non-electrolytes.

Back 17

Electrolytes: Substances which dissolve in water to produce conducting solutions of ions (e.g. NaCl)

Non-electrolytes: Substances which neither dissociate nor produce ions in aqueous solutions. (e.g.sucrose)

Strong electrolytes dissociate completely in aqueous solutions, α ≈ 1

Weak electrolytes dissociate only partially, α << 1.

Front 18

Give the definitions of acids and bases by Brønsted-Lowry and also by Lewis.

Back 18

Brønsted-Lowry: Acids are proton donor molecules or ions. Bases are proton acceptor particles.

Lewis: Acids are electron pair acceptor molecules or ions. Bases are electron pair donors.

Front 19

Give the definition and possible range of the term: degree of dissociation. Write the definition of the acid dissociation constant of a weak acid (HA).

Back 19

Degree of dissociation is the ratio of the number of the dissociated particles and the total number of particles.

0 ≤ α ≤ 1

Ka = [H+][A-]/[HA]

Front 20

Define the chemical equilibrium constant for a general equilibrium system. Write an equation (mass action law) and explain the denotations.

Back 20

Front 21

What does the Le Chatelier-Braun principle state?

Back 21

When a system in equilibrium experiences a stress (e.g. change in the concentration, temperature,or in case of gases pressure), a new equilibrium is settled that relieves stress.

Front 22

Give the value of the water ion product at 25°C! Define the terms pH and pOH and give their relationship.

Back 22

Front 23

What do buffer solutions consist of? Define the terms: buffer effect and buffer capacity.

Back 23

Composition of the buffer solutions: A solution of a weak acid and its conjugate base (acidic buffer), or a solution of a weak base and its conjugate acid (alkaline buffer).

Buffer effect: Diminishes changes in pH when acid or base is added.

Buffer capacity: The amount of a monoprotic, strong acid (e.g.HCl) or monobasic, strong base (e.g. NaOH) in moles that should be added to one litre of buffer in order to change the pH of the bufferby one unit.

Front 24

Write the Henderson-Hasselbach equation and explain the denotations!

Back 24

Front 25

Characterise the chemical bonds that hold the metal ions and the ligands together in metal complexes.

Back 25

In the complexes a special covalent bond, the so called dative (coordinative) bond is present. In this bond both bonding electrons are donated by the ligand and accepted by the metal ion. If one ligand donates more than one bonding pair to the same metal ion, than a quite stable, so called chelate complex is formed.

Front 26

Define the terms: exothermic, endothermic, exergonic and endergonic processes.

Back 26

In an exothermic process the enthalpy of the system decreases ( the enthalpy of the products is smaller than the enthalpy of the reactants), ΔH < 0 the energy is released in the form of heat, whereas the enthalpy of anendothermic process increase, ΔH > 0.

if ΔG < 0 the reaction happens spontaneously, it is exergonic

if ΔG > 0 the reaction does not go spontaneously, it is endergonic

Front 27

Write the Gibbs equation with the explanation of the denotations. Give the relationship between the direction of the processes and the sign of the free energy change.

Back 27

Front 28

Depict the transition state and the activation energy of a reaction in a graph. What is thedefinition of a catalyst?

Back 28

The catalyst opens a new reaction route with a lower activation energy and thus accelerates the reaction.

Front 29

Define the terms: oxidation, reduction, oxidizing agent, reducing agent.

Back 29

oxidation: loss of electrons

reduction: electron uptake

oxidizing agent: takes electrons from other substances

reducing agent: gives electrons to other substances

Front 30

Write the Nernst equation of the electrode potential with the explanation of the denotations.

Back 30

Front 31

Draw a galvanic/voltaic cell, write its cell diagram and define its electromotive force.

Back 31

(-) Zn(s)|Zn2+||Cu2+ |Cu(s) (+)

Eel = εk-εa

Eel : electromotive force

εk and εa : electrode potentials of the cathode and the anode, respectively.

Front 32

Draw with structures three molecules (not ATP) containing high energy phosphate bonds.Circle the high energy phosphate bonds.

Back 32

1) 1,3-bisphosphioglycerate

2) phosphoenolpyruvate

3) creatine phosphate

Front 33

Describe briefly the molecular explanation of the toxicity of cyanide ions and carbonmonoxide, respectively.

Back 33

Carbon monoxide binds strongly to hemoglobin and prevents the binding of oxygen.

Cyanide bind to the heme in cytochrome oxidase (Complex IV) and inhibits its normal function

Front 34

Give the essential components and the osmolarity of the Ringer’s solution.

Back 34

Na+, K+, Ca2+, Cl-

305-315 mOsm

Advanced versions may contain acetate, lactate, bicarbonate.

Front 35

Define the term: constitutional isomerism. Give examples!

Back 35

The constitutional isomers differ in the connection order of their atoms.

Front 36

Define the term: configurational isomerism. Give examples!

Back 36

The configurational isomers differ in the relative steric position of the substituents.

Front 37

Define the term: conformational isomerism. Give examples!

Back 37

The conformational isomers form as a result of the rotation around sigmabond(s).

Front 38

Define the terms: enantiomers, diastereomers. Give chiral examples.

Back 38

Two non-super imposable stereoisomers that are mirror images of each other are called enantiomers.

Stereoisomers which are not mirror images of each other are called diastereomers.

Front 39

Draw with structure a primary alcohol, a secondary alcohol, a tertiary alcohol, an enol and a phenol.

Back 39

Front 40

Name the products of the oxidation of aldehydes (1), the reduction of aldehydes (2) and the reduction of ketones (3), respectively. Name the products of the reactions of aldehydes with primary amines (4), alcohols (5) and aldehydes (6), respectively.

Back 40

1. carboxylic acid

2. primary alcohol

3. secondary alcohol

4. Schiff’s base

5. hemiacetal

6. aldol

Front 41

Draw with structures a primary amine, a secondary amine, a tertiary amine, a quaternaryammonium salt. Give the order of base strengths of the amines in aqueous solution.

Back 41

Front 42

Draw with structures cholin, colamine and acetyl choline.

Back 42

Front 43

Draw with structures urea, guanidine and creatinine.

Back 43

Front 44

Draw with structures pyrrole and imidazole. Characterize their acid-base properties.

Back 44

Front 45

Draw with structures pyridine, pyrimidine, indole and purine. Give the numbers of theatoms also.

Back 45

Front 46

Define the term: alkaloid.

Back 46

Alkaloids are a group of naturally occurring compounds that contain mostly basic nitrogen atoms and possess physiological and/or pharmacological activities.

Front 47

Draw the structure of the reduced glutathione. Circle the part of the molecule responsible for its antioxidant property.

Back 47

Front 48

Give the definition and two most frequently used units of enzymatic activity.

Back 48

The activity of an enzyme equals to the amount of substrate transformed by the enzyme within a unit time at 25°C.

Units:

- Unit (U): μmol/min

- katal: mol/s

Front 49

Write the Michaelis-Menten equation with the explanation of the denotations.

Back 49

Front 50

Draw the structural formula of cholesterol, Give the numbers of the atoms also.

Back 50