QRC GenChem and Basic Laboratory

Element

Classify whether it is element, compound, homogenous or heterogenous mixture: A shiny, silvery-colored solid that conducts electricity and cannot be broken down into simpler substances by chemical means.

Compound

Classify whether it is element, compound, homogenous or heterogenous mixture: A clear liquid boils at 78C and remains unchanged in composition during boiling

Heterogenous mixture

Classify whether it is element, compound, homogenous or heterogenous mixture: A substance made up of two components that can be separated by filtration.

Homogenous mixture

Classify whether it is element, compound, homogenous or heterogenous mixture: A blue liquid with a uniform composition and boils at a constant temperature and cannot be separated into simpler means.

Intensive properties

Are physical properties that are independent of the amount of substance

Extensive properties

Are physical properties that are dependent of the amount of substance. Notation: “If you double the mass, will the quantity be doubled too?“

Intensive

Classify whether extensive or intensive property: Density

Intensive

Classify whether extensive or intensive property: Molar mass

Intensive

Classify whether extensive or intensive property: Boiling Point

Intensive

Classify whether extensive or intensive property: Specific Heat Capacity

Plasma

It is a state of matter that is composed of ions and free electrons, and is commonly found at very high temperatures such as stars and lightning.

Systeme Internationale d’Unites

What is the French term of SI Units?

Dalton proposed a billiard ball model

What does a Dalton’s model of atom look like?

George Stoney

He proposed that electricity is made up of negatively-charged particles (electrons).

Sir William Crookes

He stated that the cathode rays carry a negative charge.

Eugene Goldstein

He used cathode ray to study canal rays, which had electromagnetic properties opposite to those of an electron.

Henri Becquerel

He discovered radiation by studying the effects of uranium on photographic film.

Frederick Soddy; Margaret Todd

___ discovered that there appeared to be more than one element at certain positions on the periodic table. The term isotope was coined by ___ as a suitable name for these elements.

Richard Abegg

He discovered that noble gases have a stable electron configurations.

Heins Geiger

He developed a device that can detect alpha particle.

Law of Triads (Johann Dobereiner)

Is a law proposed for the arrangement of periodic table of elements where the atomic weight of the middle element should be the average of the atomic weights of the other two elements.

Law of Octaves (John Newlands)

Is a law proposed for the arrangement of periodic table of elements where every eighth elements have similar properties

Lothar Meyer

He proposed that the arrangement of periodic table of elements should have periodic recurrence.

Henrey Moseley

He discovered that the wavelengths of X-ray emission from elements corresponded to their atomic number.

Alkali Metals

Are soft, silvery metals that react vigorously with water to form M-OH and H2 gas. It is found naturally only in compounds.

React with water with exceptions: Be does not react with water and Mg is slow

What is the reactivity of G2A elements with water?

Lanthanides

Are f-block metals that form +3 cations and are found in earth’s crust (that’s why it is called as rare earth metals)

Actinides

Are f-block elements which have many oxidation states and are radioactive

Rutherfordium (104Rf) to Oganesson (118Og)

What elements are highly radioactive, synthetic transactinides

Diamond

It is an allotrope of carbon which is characterized as the hardest known natural material.

Graphite

Is an allotrope of carbon made up of layers of hexagonal sheets

Fullerenes

Are a family of carbon allotropes characterized by hollow, cage-like structures composed of carbon atoms arranged in pentagonal and hexagonal rings (e.g. C60)

Carbon nanotubes

It is a cylindrical graphene sheet.

Mercury, Gallium, Francium, and Bromine

What elements are liquid at room temperature

International Union of Pure and Applied Chemistry

IUPAC means

Ox SilA Fe

Oxygen, Silicon, Aluminum, and Iron

What elements does Earth’s crust contain?

Ox Ca? HydNi

Oxygen, Calcium, Hydrogen, and Nickel

What elements does human body have?

Cis STOP: Carbon, Sulfur, Tin, Oxygen, and Phosphorus

Semiconductors

Some metal and non metals

What elements have allotropes (they are 5 only)

D.

A vessel contains an equilibrium mixture of NO2(g) and N204(g) at a fixed temperature and a total pressure of 1.00 bar, as shown below. Which diagram best represents the system at equilibrium after argon is added, while maintaining both the temperature and the total pressure constant?

A.

B.

C.

D.

(a) no shift
(b) shifts toward more moles of gases

What is the effect on equilibrium when an inert gas is added in a condition where there is:

(a) constant volume
(b) constant pressure

Solvation

It is the interaction of any solvent with ions or molecules.

Henry’s Law (S=k_HP)
As pressure increases, solublity increases
As temperature increases, solubility decreases

Why? A_(g) ⇌ A_(aq) + ∆ – Solubility of gas in liquid is exothermic, so as temperature increases, equilibrium shifts toward the gas, decreasing its solubility.

What is the principle behind the effects of pressure and temperature to the solubility of gas in liquid?

Soft drinks are cabonated drinks that contain no alcohol, which could be an alternative to beer, wine, or other alcoholic drinks (Hard drinks)

What is the difference between soft drinks and hard drinks?

Transuranium elements

These are significantly synthetic elements that are usually radioactiv and often have very short half-lives.

(a) Hemihydrate

(b) Sesquihydrate

Hydrates can have fractional moles of water molecules. What is the prefix used for hydrates if it has (a) 0.5H2O, and (b) 1.5H2O?

Stoichiometric point (characteristic of increasing concentration of product, but at this point, it becomes a plateau due to all limiting reactants being used up)

It is the point in a chemical reaction at which the reactants are present in the exact mole ratio required by the balanced chemical equation.

Reverse rxn, Forward rxn, and system is at equilibrium

What reaction is favored if Q>K, Q<K, and Q=K?

G1A, Acetates, Nitrates, and Ammonium are always soluble
G17 are soluble except Pb, Hg, Ag
Sulfates are soluble except Ba, Ca, Sr, Pb, Hg, Ag
Hydroxides are insoluble except Ba, Ca, Sr
Sulfides are insoluble except bonded with G1, G2, and NH4
Carbonates, chromates, and phospates are insoluble except when bonded with G1 and NH4

What are the solubility rules for G1A, G17, Sulfides, Acetates, Nitrates, Ammonium, Chromates, Carbonates, Phosphates, Hydroxides, and Sulfates?

Na2CO3 (soda ash)
K2CO3 (potash)

When saponin-rich plants are burned, they produce ashes rich in salts like ___ and ___. State their common names as well.

Strong monoprotic acid: H₃O⁺ = A<sup>–
* HA is not included because since it is strong, there is complete ionization</sup>
Strong polyprotic acid (H₂SO₄): H₃O⁺ > HSO₄^– > SO₄^2–

In ranking the concentrations of all species present in a strong acid, how is it arranged for monoprotic and polyprotic acids?

Weak monoprotic acid: HA > H₃O⁺ = A^– > OH^–
Weak polyprotic acid (H₂CO₃): H₂CO₃ > H₃O⁺ > HCO₃^– > CO₃^2– > OH^–

In ranking the concentrations of all species present in a weak acid, how is it arranged for monoprotic and polyprotic acids?

(Use a ladder diagram)

The most dominant species is HCO₃^–

Carbonic acid has two ionizable protons, where Ka1=4.5×10^–7 and Ka2=4.7×10^–11. What is the most dominant species at pH of 7?

A. 0.15 = [HClO₂] + [ClO₂^–]

B. 0.10 = [H₃PO₄] + [H₂PO₄^–] + [HPO₄^2-] + [PO₄^3–]

C. 0.20 = [Mg²⁺]; 0.40 = [Br^–]
2[Mg²⁺] = [Br^–]

What is the mass balance equation of the ff.:

A. 0.05M HClO₂ and 0.10M NaClO₂
B. 0.10M H₃PO₄
C. 0.20M MgBr₂

C_HA = [HA] + [A^–]

What is the formula for mass balance equation?

MBE: 0.10M = [Na⁺]
0.10M = [H₂CO₃] + [HCO₃^2–] + [CO₃^2–]

CBE: [Na⁺] + [H₃O⁺] = [HCO₃^2–] + 2[CO₃^2–] + [OH^–]

What is the MBE and CBE for 0.10M NaHCO₃?

Multiply to the charge

For writing CBE, what is the important rule to remember if the charge of a species is not 1?

Use mass balance equation:

To calculate the pH of a specific concentration of an acid, how can you calculate it?

For instance, you are asked of the pH of 1×10^–8M HCl.

What are the cations, reagent used, and confimatory tests for Group 1 cations?

What are the cations, reagent used, and confimatory tests for Group 2 cations?

What are the cations, reagent used, and confimatory tests for Group 3 cations?

What are the cations, reagent used, and confimatory tests for Group 4 cations?

What are the cations, reagent used, and confimatory tests for Group 5 cations?

Florence Flask

Thiele tube

Capillary Tubes

Separating funnel

Dropping Funnel

Distilling Flask

Condenser

Fractionating Column

Distillation adapters

0.0001g

What is the typical precision of analytical balances?

weighing by difference

For hygroscopic substances, what is the preferred technique for getting its mass?

Buret

It is a precision glass tube with graduations used to measure the volume of liquid dispensed through a stopcock.

1. Volumetric buret: Uses a stopcock and relies on gravity to dispense liquid manually

2. Digital buret: Uses a manual plunger to deliver liquid

3. Electronic buret: Relies on automated dispensing

What are the 3 types of buret? What are their characteristics?

Condensers convert vapor to liquid, while fractionating column separates two liquids with almost similar boiling points.

Differentiate condenser and fractionating columns?

HNO₃ and HCl

Aqua regia is a 1:3 mixture of ___ and ___.

Pipet

It permit the transfer of accuratelt known volumes from one container to another.

Volumetric: Delivers fixed volume
Serological Pipet: Blow-out type
Mohr pipet: Drain-out type
Micropipet: Delivers smaller volumes

Laboratory pipets include volumetric, serological, mohr, and micropipets. Differentiate each.

The pipet can deliver volumes from 1–100mL volumes, it is class A (of higher accuracy), and ±0.5 uncertainty

What does the markings indicate?

Population

In sampling, it is the entire group of individuals or items or data points under study.

Sample

It is the subset of a population selected for analysis.

1. Simple random: Every sample unit has equal chances of being chosen
2. Systematic: Every nth sample unit is chosen
3. Stratified: Population is divided into sub-group (strata), and a sample unit is chosen from each group
4. ClusterPopulation is divided into clusters, and all/some can be chosen

In probability sampling techniques, how are these techniques done:
1. Simple random
2. Systematic
3. Stratified
4. Cluster

1. Convenience: Sample unit is taken that is easy to access
2. Judgmental: Sample unit is judged to be useful for study
3. Quota: Population is grouped, and a specific number of sample units are chosen from each group
4. Snowball: One sample unit recruits future sample unit

In non-probability sampling techniques, how are these techniques done:
1. Convenience
2. Judgmental
3. Quota
4. Snowball

Gross Sample

It is a large, initial portion collected from various parts of the population. It is meant to capture overall variability and is often too large to analyze directly.

Laboratory Sample

A portion taken from the gross sample that is homogenized and already processed.

Grinding

It is a method of reducing particle size which reduce crushed material into fine powder.

Milling

It is a method of reducing particle size which produce uniform fine particles.

Ball MillingI

It is a process where material is palced in a rotating container with balls to grind it into finer particles.

Cryogenic Grinding

It reduces particle size by freezing the material with liquid nitrogen before grinding.

Dry Ashing

It involves high-temperature incineration in a muffle furnace where water and volatiles are vaporized, leaving organic matter.

Wet Ashing

It involves treating the sample with acids (or bases) in an open container and heated on a hot plate to break down organic matter while keeping minerals dissolved in the solution.

Microwave Digestion

It is a digestion process used to dissolve organic and inorganic samples for trace metal analysis.

Fusion

It is a digestion proces where inorganic samples are often dissolved using a large excess of an alkali metal salt called as flux. The sample is mixed with the flux, heated until molten, and cooled at room temperature where the resulting melt dissolves easily in water/acid.

Swirl it gently, let it sit undisturbed for few minutes, and add ethanol to break the emulsions.

In liquid-liquid extraction, what will you do when emulsions exist?

Diethyl ether, DCM, hexane, and toluene

What are the common solvents used in LLE that are immiscible with water?

Recrystallization

It is the primary method for purifying non-volatile organic solids due to its effectivity in separating a desired compound from impurities based on differences in solubility.

Hot gravity filtration is dispensing the hot solution into a stemless funnel with fluted filter paper to remove impurities.

Vacuum filtration is collecting the crystals using a Buchner funnel with a filter paper, where a vacuum draws the solution out.

Differentiate hot gravity filtration with vacuum filtration.

A Thiele tube uses a flame-heated oil bath where the sample in a capillary is heated by convection and the melting temperature is read from a thermometer. A Mel-Temp uses an electrically heated metal block to heat capillary samples at a controlled rate with a digital readout, while a Fisher-Johns apparatus heats a tiny sample placed between glass plates on a hot stage and allows direct microscopic observation of melting.

Differentiate how Thiele tube, Mel-Temp apparatus, and Fisher-Johns apparatus work for melting point determination.

Distillation

It is a key separation technique in the laboratory, widely used to purify liquids and separate mixtures based o difference in boiling points.