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30.9.17

Formula unit of NaCl, sodium chloride


Formula unit of NaCl, sodium chloride


The compound sodium chloride consists of Na+and Cl- ions held together by electrostatic forces of attraction in a very large ordered network called a crystal. The hypothetical combination of the one Na+ and one Cl- ion indicated is a formula unit. It is the smallest collection of ions from which we can deduce the formula NaCl.


Formula unit of NaCl, sodium chloride
Formula unit of NaCl, sodium chloride


Tage: sodium chloride, NaCl, empirical formula, electrostatic, salt
Source:
Freefullpdf for Scientific Publications

Symbols & periodic table locations of some monatomic ions


Symbols & periodic table locations of some monatomic ions


In general, (a) the metals of Groups 1A and 2A and aluminum have just one cation, which carries a positive charge equal in magnitude to the A-group number; 
(b) the metals of the B-group have two or more cations of different charges, though in some cases only one of these cations is commonly encountered; and 
(c) the nonmetals of Groups 7A and 6A, nitrogen and phosphorus form anions with a charge equal to “ the group number minus eight.” l

Symbols & periodic table locations of some monatomic ions
Symbols & periodic table locations of some monatomic ions


Symbols & periodic table locations of some monatomic ions

Scheme based on the periodic table to assist in writing formulas



Scheme based on the periodic table to assist in writing formulas

The lines trace a continuous path from boron (B) to fluorine (F). 

The element that is generally written first in the formula of a binary molecular compound is the one that is closer to the beginning of this path






Tage: periodic table, naming, binary compounds

Source:
Freefullpdf for Scientific Publications

29.9.17

Dalton's atomic weight problems



Dalton's atomic weight problems

Dalton assumed a combining ratio of hydrogen to oxygen atoms of 1:1. 
Data at the time suggested that the mass ratio of hydrogen to oxygen in water was 1:7. Taking the atomic weight of hydrogen to be one, that of oxygen was seven. 

Modern data indicate that the combining ratio of hydrogen to oxygen atoms is 2:1 and that the mass ratio is 1:8 (or 2:16). 

If the atomic weight of hydrogen is taken to be one, that of oxygen must be 16.

see also: Dalton's theory and conservation of mass

Dalton's atomic weight problems




Tage:

the law of multiple proportions, Dalton, atomic mass, water, mass percent
Source:
Freefullpdf for Scientific Publications

Dalton's theory and conservation of mass


Dalton's theory and conservation of mass

Dalton's theory explained these two basic laws of the chemical combination as described in the text. If six fluorine and four hydrogen atoms are available before the reaction, the 10 atoms will still be present in the products, in this case, four HF molecules and one unreacted fluorine molecule.

Dalton's theory and conservation of mass


see also:

Dalton's theory and conservation of mass

Illustration of the Law of Definite Proportions


Keywords
conservation of mass, Dalton, stoichiometry, chemical reactions
Source:
1-Freefullpdf for Scientific Publications

Calculations illustrating the law of multiple proportions


Calculations illustrating the law of multiple proportions

The oxygen-to-carbon mass ratio in carbon dioxide is twice that in carbon monoxide.


Calculations illustrating the law of multiple proportions

see also:

Illustration of the Law of Definite Proportions

Difference between accuracy and precision by an image


Tage: multiple proportions, calculations, stoichiometry, Dalton

Source:
Freefullpdf for Scientific Publications

Illustration of the Law of Definite Proportions


Illustration of the Law of Definite Proportions

Basic copper carbonate occurs in nature as the mineral malachite
(a), it forms as a patina on copper roofs
(b) and bronze statues, and can also be synthesized in the laboratory
(c). Regardless of its source, basic copper carbonate has the same composition.

Illustration of the Law of Definite Proportions, law of definite proportions, Proust, copper carbonate, malachite, redox, law of constant composition
The Law of Definite Proportions

Also, you can see general chemistry posts


see also:

The law of definite proportions, Proust, copper carbonate, malachite, redox, the law of constant composition

22.9.17

chemdraw online


ChemDraw is the best chemistry software for students

ChemDraw and Sketcher are the drawing tool online of choice for creating publication-ready, scientifically. online chemical databases and viewing and publishing online structures

There are two types of ChemDoodle Web Sketchers, the Full Sketcher, and the Single Molecule Sketcher. You can choose either above in this demo. Based on the interface, you may be using one or the other or both. The Full Sketcher allows for the creation of multiple chemical structures, shapes, and figures. The Single Molecule Sketcher provides a streamlined interface for drawing a single molecular structure

The introduction tutorial to the ChemDoodle Web Sketcher















source:chemdoodle

9.9.17

difference between accuracy and precision by image


Precision and accuracy

Comparing precision and accuracy: a dart board analogy

The accuracy and precision of darts hitting a dart board illustrate the ways that data can be precise and/or accurate.
(a) The darts are both scattered (low precision) and off-center (low accuracy). 
(b) The darts are in a tight cluster (high precision) but still off-center (low accuracy). 
(c) The darts are somewhat scattered (low precision) but evenly distributed about the center (high accuracy).






Keywords
precision, accuracy, measurements, data, dart
Source:
1-Freefullpdf for Scientific Publications

difference between fahrenheit and celsius degrees


The thermometer on the left is marked in degrees Celsius and the one on the right in degrees Fahrenheit. The freezing point of water is at 0 ¡C and 32 ¡F; the boiling point is at 100 ¡C and 212 ¡F. 

Note that for an interval of 10 ¡C, the corresponding interval on the Fahrenheit scale is 18 ¡F. 

This gives rise to the factor 18/10 = 1.8 in the equations that relate the two scales.