Chemistry 1: Pre-Exam Questions

Isotopes

Atoms of the same element with same proton number but different neutron number, thus have different mass number.

Same atomic number; different mass number

Valence electrons

Electrons in the outermost shell of an atom

What does exothermic mean?

Process where energy is released into the surroundings from the system resulting in a negative enthalpy change.

What does endothermic mean?

Process where energy is absorbed from the surroundings into the system resulting in a positive enthalpy change.

Heat of combustion

Heat is released when a substance undergoes complete combustion with oxygen under standard conditions.

Chemical compound

A substance composed of atoms held together by chemical bonds.

Conditions of hydrogen bonding

Hydrogen must be attached to a highly electronegative atom that has lone pairs (N, O, F).

Chlorine-containing disinfectant

NaOCl - Sodium hypochlorite

Ca(OCl)2 - Bleaching powder

Disinfectants not containing chlorine

I2 and H2O2 (Iodine, hydrogen peroxide)

Ions causing water hardness

Calcium (Ca2+)

Magnesium (Mg2+)

Heavy water?

Water in which hydrogen atoms are replaced with deuterium.

What does bleach contain?

NaOCl

What is bleaching powder?

Ca(OCl)2

Gaseous neurotransmitters

NO, CO, H2S

Factors influencing solubility of gases

Pressure and Temperature

What is osmosis?

The flow of a solvent through a semipermeable membrane from a region of high water potential to low water potential.

What is osmotic pressure?

The external pressure needed to stop osmosis

Isotonic solution

Solute concentration is the same as the cells

= Cells remain same size

Hypertonic solution

Higher solute concentration than inside the cell, resulting in water moving outwards = Cells shrink

Hypotonic solution

Lower solute concentration than inside the cell, causing water to move inwards = Cell swells

Define reaction rate

Change in concentration per unit time

Factors influencing reaction rate

Temperature

Concentration

Catalyst

Half-life of a reaction?

Time required for the concentration of a reactant to decrease to half its initial value

What is a catalysis?

A catalyst speeds up the rate of the reaction by providing an alternative pathway

What is a catalyst?

A substance that increases the reaction rate by providing an alternative pathway with lower activation energy and it is not used up.

What is inhibition?

A substance slows down the reaction.

What is electrolysis?

Conversion of electrical energy into chemical energy

Basis of galvanic cells

Conversion of chemical energy into electrical energy

What is oxidation?

Loss of electrons

What is reduction?

Gain of electrons

What is the corrosion of a metal?

Chemical/electrochemical degradation of metal usually through oxidation

When does a local cell form?

When 2 parts of the metal surface have different potentials.

What is an inhibitor/catalytic poison?

A substance that decreases the activity of a catalyst by occupying its active site

Autocatalysis?

One of the reactions products acts as a catalyst to accelerate the reaction.

Homogeneous

Catalyst in same phase

Components are evenly distributed

Heterogeneous

Catalyst in different phase

Components aren’t uniform/evenly distributed

What is a chelate complex?

A complex where one ligand binds to a metal atom through multiple donor sites.

Macrocyclic chelate?

Coordination complex where the ligand is a large ring-shaped multidentate ligand, forming highly stable chelate rings.

How does a liquids boiling point depend on external pressure?

Higher the external pressure, the higher the boiling point.

Equilibrium vapor pressure?

pressure of the vapor that is in equilibrium with its liquid at a given temperature.

What is a weak acid?

Does not dissociate completely

What is a strong acid?

Dissociates 100% (completely)

Use of buffer solutions

To maintain pH nearly constant

Composition of a buffer

Weak acid and its conjugate base

Buffer examples

NH4+Cl-/NH3

Hydrolyzing salt

A salt whose ions donate/accept protons from water

Strong acid examples

HCl, H2SO4, HNO3

Weak acid examples

CH3COOH, H2PO4, H2CO3

Weak bases

NH3

N2H4

Strong bases

NaOH

Ba(OH)2

KOH

Lewis acids

Fe3+ , BF3

Lewis bases

OH

NH3

Define colloidal systems

A system containing particles in 1-500um size range

What is emulsion?

Colloid where both dispersed phase and medium are liquids

What is suspension?

Colloid where the dispersed phase is solid and the medium is liquid

What is hydration?

Water molecules surround dissolved particles

What is adsorption?

Binding of a substance onto the surface of another.