Notes, abstracts, papers, exams and problems of Chemistry

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Laws ponderal

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pure substance: is a phase of uniform composition and unchanging can not be decomposed into other substances of different classes by physical methods.

elements: they are pure substances that can not be decomposed into simpler ones through normal chemical processes.

compounds: they are pure substances made up of two or more elements, which can be decomposed by chemical methods on the elements of which are constituted. A compound always has the same elements and the same proportions regardless of the process followed.



Blended is an aggregation of different substances without causing any chemical reaction between them and therefore may be separated by physical methods.

ponderal laws: they refer to the quantity of matter of different substances... Continue reading "Laws ponderal" »

Farmaco

Classified in Chemistry

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Digestive system drugs
Mucosal protective:
· Sulcralfato: not absorbed form film on the surface of the stomach, protects against erosion of the wall, prevents ulcers, and promotes healing.
· Carbenoxolone: active principle of liquorice. It stimulates the secretion of stomach wall mucus, the mucus is thicker and adheres well to the wall protecting it. It is absorbed in the digestive tract fluid retention and edema. It is contraindicated in hypertensive patients.
Secretion inhibitors:
· H2 antihistamines: HCL inhibits secretion. Used cimetidine. Ranitidine and famotidine, are indicated in gastric or duodenal ulcer, oesophagitis. They can give diarrhea or constipation, dizziness.
· Inhibitors hydrogen bomb: Omeprazole. H inhibits the... Continue reading "Farmaco" »

chem final

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Chem Cheat Sheet

Mol = M*L

m = mol/Kg

Strong Acids

HCL hydrochloric

H2SO4 sulfuric

HNO3 nitric

HBR hydrobromic

HI hydroiodic

HCLO4 perchloric

Cp H2O (l) = 4.184

Cp H2O (s) = 2.03

Cp H2O (g) = 1.998

ΔHfusion of H20 = 6.02

ΔHvap of H20 = 40.7



Boiling/melt pt

volatility

Solubility in water

conductivity

examples

Network Cov

Very high

Very low

insoluble

non-conduct

diamond

Ionic

Very high

Very low

Very soluble

Conducts if L or G

salt

metallic

Mostly high

Very low

insoluble

Good conduc

gold

H-bonding

Relativly high

Relativly low

Very soluble

Non conduct

water

Dipole dipole

moderate

moderate

Mostly sol

Non conduct


LDF

Very low

Very high

insoluble

Non conduct



Moles a militros

Posted by Gorethog and classified in Chemistry

Written at on English with a size of 2.63 KB.

N = the number of particles

NA = 6.02*10^23 particles/mol

n = moles

N = n * NA

mass / molar mass = mol

n = N /NA

percent composion of s = mass of s / mass of compund *100

Identifying limiting reactant :

1) masses to moles

2)use mole ration

3) limiting reactant is the one that is with the smallest num

Percent yield:

1)Divide given yeild by the limiting reactant

2) multiply by 100

Finding the Formula of a Hydrate:

 1. Find the # of g of MN and # of g of H 2 O.

 2. Convert g to mol.

3. Divide each “# of mol” by the smallest “# of mol.”

4. Use the ratio to find the hydrate’s formula.

Mass percent of water in Ba(OH)2 . XH2O

= (Total mass of sample) - (Mass of Ba(OH)2 in sample) / (Total mass of sample)  * 100

Ba(OH)2

molar mass molecular mass /molar

... Continue reading "Moles a militros" »

Consider an atom that has an atomic number of 8 and a mass number of 17 If it has a -2 charge it contains electrons.

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ATOMS

the nucleus which is at the middle of the atom- contains protons and neutrons, has positive charge due to protons, almost the whole mass of the atom concentrated here but it´s tiny compared to the rest pf the atom.

The electrons move around the nucleus in enery levels called shells- they are negatively charged, they´re tiny but they cover a lot of space, the size of their orbit determines how big the atom is and they have virtually no mass.
      PROTONS ARE HEAVY AND POSITIVELY CHARGED 
                  NEUTRONS ARE HEAVY AND NEUTRAL
ELECTRONS ARE TINY AND NEGATIVELY CHARGED 

atomic number tells you how many protons there are (bottom number)

Atoms of the same element all have the same number of protons- so atoms of different
... Continue reading "Consider an atom that has an atomic number of 8 and a mass number of 17 If it has a -2 charge it contains electrons." »

Polarized covalent bond

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- Hydrogen bonding will be much stronger with H2O because H2O forms a ring like structure due to high ability of hydrogen bonding. In the other hand, ammonia's hydrogen bonding is limited due to having 3 hydrogen atoms. Nitrogen has only one lone pair that cant satisfy all 3 hydrogens. Therefore, H20 has a stronger bonded structure.

- a) magnesium, b) chlorine, c) Vanadium, d) Rubidium

- Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Conceptually, ionization energy is the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation. Therefore, the higher this energy is, the more unlikely it is the atom becomes a cation. When moving to the right

... Continue reading "Polarized covalent bond" »

mmmm

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1. ABODE: a place in which a personresides

2.PLASTERING:a coatingofplaster.
3.CHINKS: a crack,cleft, or fissure
4.CHIMNEY: a structure containing a passage by which the gasesarecarriedoff
5.HEWN:felledandroughlyshaped by hewing
6.STUDS: small pieces of metal
7.DEW: moisturecondensedfromtheatmosphere,especially at night
8.EXUDE: to comeoutgradually in drops, as sweat
9.MIST:watersuspended in theatmosphere
10.RIPPLES:to formsmallwaves or undulations
11.ROUT:anyoverwhelmingdefeat
12.SWATH:thepiece or strip so cut
13.MEANNESS: thestateorqualityofbeingmean.
14.HASTILY: made or donewithhaste or speed
15.WINDOW CASING: border of the window
16.CLOUT:long hit
17.SUPERLUOUS: unnecesary
18.WRETCHEDNESS: misery, misfortune
19.
... Continue reading "mmmm" »

Who said "the total mass of reactants equals the total mass of the products"

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1. Alkali metal (Group IA) compounds are soluble.

2. Ammonium (NH4+) compounds are soluble.

3. Nitrates (NO3-), chlorates (ClO3-), and perchlorates (ClO4-) are Soluble.

4. Most hydroxides (OH-) insoluble EXCEPT alkali metal hydroxides And Ba(OH)2. Ca(OH)2 is slightly soluble.

5. Most chlorides (Cl-), bromides (Br-) or iodides (I-) are soluble. EXCEPT those containing Ag+, Hg+2, and Pb+2.

6. Carbonates (CO3-2), phosphates (PO4-3) and sulfides (S-2) are Insoluble. EXCEPT alkali metals and ammonium ion.

7. Most sulfates (SO4-2) are soluble. CaSO4 and Ag2SO4 slightly soluble. BaSO4, HgSO4 and PbSO4 insoluble.


Strong Acids: /// Partial Pressure: (P1+P2+P3…) or (n1+n2+n3...)(RT/V)

HCl - hydrochloric acid /// Avogadro's # 6.0221415 × 1023 Mol-1

HNO3... Continue reading "Who said "the total mass of reactants equals the total mass of the products"" »

Intermolecular forces essays

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- Without H20 being polar, there would be no life on Earth, and Earth will be very dry. Humans and living organisims depend on H20 and it's polarity to sustain life on Earth because h20 wouldnt be able to form hydrogen bonds because it isnt polar. Animals who depend on ice such as polar bears and seals wold not be able to live due to ice not floating on the surface of water. When ice lacks crystal lattice structure, it starts to drown, and this happens due to the lack of hydrogen bonding. Therefore, h20 is very important for life to exist on earth.

- h-h: nonpolar covalent bond

- p-cl: covalent

- na-br: ionic

Electronegativity: 0->0.4 = covalent, 0.5->1.7=polar covalent, more than 1.7= ionic bonds, minus the EN

- Ion-induced dipole force:

... Continue reading "Intermolecular forces essays" »

Properties of gases(diffusion and pressure)

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Chem Cheat Sheet

Mol = M*L

m = mol/Kg

Strong Acids

HCL hydrochloric

H2SO4 sulfuric

HNO3 nitric

HBR hydrobromic

HI hydroiodic

HCLO4 perchloric

Cp H2O (l) = 4.184

Cp H2O (s) = 2.03

Cp H2O (g) = 1.998

ΔHfusion of H20 = 6.02

ΔHvap of H20 = 40.7

1.An amorphous solid still has all the properties of a solid except for its ___________ _______________:disorganized arrangement

2.At STP, 1 mol =:22.4L

3.At STP, P=:1atm

4.At STP, T=:273K

5.avogadro's number:6.0221409x10^2

6.Boyle's Law:PV=PV (inversely proportional - as P↑, V↓)

7.Charles' Law:V/T = V/T (directly proportional - as P↑, V↑)

8.Combined Gas Law:PV/T = PV/T (T must be K, everything else whatever)

9.Dalton's Law of Partial Pressure:Pressure(total) = Pressure(a) + Pressure(b)

10.Equation for solving phase changes

... Continue reading "Properties of gases(diffusion and pressure)" »