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General Chemistry

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Downloads to date: N/A | Words: 215 | Submitted: 04-Sep-2011
Spelling accuracy: 29.3% | Number of pages: 2 | Filetype: Word .doc

Description

General Chemistry; formulas, moles etc

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WRITING FORMULAES

POSITIVE IONS NEGATIVE IONS


1
2
3
NH4+
H+
Mg2+
Al3+

Na+
Ca2+
Fe3+

K+
Sr2+



Ba2+



Fe2+



Zn2+



Cu2+


6
7
PO43-
O2-
F-

S2-
Cl-
OH-
SO42-
Br-
NO3-
CO32-
I-
NCO3-


HSO4-



MOLES

M = Concentration in mol/dm-3

A mole is a measure of a substance that contains the same number of particles/atoms as in 12g of carbon.
In other words, it is the RAM (Relative Atomic Mass), also known as the big number.

12g of carbon atom contains 6.02x1023
1 mole = 6.02x1023
6.02x1023 is known as Avogadro’s number

Example
Calculate the number of moles of Calcium Hydroxide reacted with 0.0642 moles Nitric acid?

Ca(OH)2 + 2HNO3 à Ca(NO3)2 + 2H2O
1 : 2
0.0321 : 0.0642




Molar mass = RAM = weighted mean mass of atom/element
1/2th mass of Carbon-12 atom

To calculate RAM from Mass Spectrometry;

RAM = Mass x Relative Abundance

ENTHALPY

Enthalpy – The energy during a chemical reaction in a system at standard pressure.



Heat gained = MC ?T

Specific heat capacity – Heat (joules) needed to increase the temperature of 1g of substance by 1oC.

Exothermic – Energy of products is less than the energy of reactants.
Endothermic – Energy of products is more than the energy of reactants.

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