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C4 Stoichiometry (Shi Yu) (Chemical equation (Word equation (1.Word…
C4 Stoichiometry (Shi Yu)
Chemical equation
Chemical equation is used to represent chemical reactions with the following general form :
reaction-->products
Arrow is used to separate reactants and products in a chemical reaction. It is read as "produce" or "generate".
Chemical equations are further classified into two types,
word
equation and
symbol
equation.
Word equation
1.Word equation represents the chemical species involved in a chemical reaction as chemical names.
2.For example, when magnesium reaction with oxygen to produce magnesium oxide, the word equation which represents such reaction is.
Reactants
are put on the left of the chemical equation while
products
produced after chemical change are placed on the right.
Symbol equation.
1.Symbol equation represents the chemical species involved in a chemical reaction as chemical formula.
2.For example, when carbon reacts with oxygen to produce carbon dioxide, the symbol equation which represents such reaction is.
3.We often indicate in the equation the physical state of the reactants and products by using the following symbols:
Solid (S), Liquid (L), gas (G)
Dissolved in water (in aqueous solution) (aq)
Balancing Chemical Equations
It is important to recognize that in a chemical reaction, atoms are neither
destroyed nor created
.
Formula
Naming binary compounds :
Binary compounds are classified into two further types:
Compounds that contain a metal and a non-metal (ionic)
Compounds that contain two non-metals (covalent)
Metal + non-metal ( ionic compound)
Naming Compounds That Contain Polyatomic Ions (Compound ions)
Common compound ions :
Ammonium 铵根 (NH4+)
Nitrate 硝酸根 (NO3-)
Hydroxide 氢氧根 (OH-)
Carbonate 碳酸根 (CO3-2)
Sulfate 硫酸根 (SO4-2)
phosphate 磷酸根 (PO4-3)
Rules for writing formula :
Each atom present is represented by its element symbol.
2.The number of each type of atom is indicated by a
subscript
written to the
right
of the element symbol.
When only one atom of a given type is present, the subscript 1 is not written.
Relative atomic mass :
Relative atomic mass (Ar) is the
average
mass of isotopes of an element compared to mass of
carbon - 12
atom.- The carbon-12 has a mass of exactly
12
units.
The mole
Avogadro's constant :
6.02 * 10^23
mass(g) =mole x Mr
volume
(\(dm^3 \)/\(cm^3 \))=
mole
x
24
(\(dm^3 \)/\(cm^3 \))**
moles=concentration(\(mol/dm^3 \)) x v/1000(\(cm^3 \))
mass=concentration(\(mol/dm^3 \)) x v/1000(\(cm^3 \))
solution:
a mixture of solute and solvent
solute(溶质):
substance that is dissolved in solvent
solvent(溶剂):
substance that dissolve solute
Finding the masses of molecules and ions :
1.Relative molecular mass (Mr) is the
sum
of the relative atomic masses in a molecule. Example. Find the Mr for following two molecules.
2.Relative formula mass (Mr) is the
sum
of the relative atomic masses in an ion or ionic compound. Example. Find the Mr for following ionic compound.