Topic 1 - Stoichiometry Flashcards
what’s the name of the phase change when solid -> Gas
sublimation
what’s the name of the phase change when solid -> liquid
melting
what’s the name of the phase change when Gas -> Solid
deposition
what’s the name of the phase change when Liquid -> Gas
boiling evaporation
what’s the name of the phase change when Liquid -> solid
freezing
what’s the name of the phase change when gas -> liquid
condensation
what are the state symbols for
solid
liquid
gas
aqueous
- (s)
- (l)
- (g)
- (aq)
what is aqueous solutions
solutions formed by dissolving a solid in a liquid
Physical change
a substance only changes from one phase to another, without forming new substance.
eg, H2O(s) -> H2O(l)
chemical changes
result in formation os new chemical substance.
the atoms in the reactants are rearranged to from new product.
facts about chemical changes refer to (Law of conservation of mass)
In a chemical reaction matter is not created or destroyed.
1, number of atoms R=P
2, atoms of reactant has been rearranged to form the product.
what are the two groups of matter
1, Pure substances
- element and compounds
2, Mixtures
- homogeneous or heterogeneous
definition of elements
Is a substance that cannot be broken down into a simpler substance by chemical means.
- all known elements can be found on the Periodic Table
definition of molecules
Electrically neutral group of two or more atoms bonded together.
H2,Cl2,N2
electrically neutral
An object that has a balance of protons and electrons.
Opposite=charged objects
Definition of compound
Formed from two or more different elements chemically joined in a fixed ratio.
eg. H2O
key fact of compounds
They have different properties from the element that they are made from.
eg. 2Na+Cl2->NaCl
chlorine poisons gas and reactive metal = table salt
Definition of mixture
They contain more that on element and/or compound that are not chemically rounded together and so
- retain their individual properties.
two types of Mixture
1, homogeneous mixture
- have a constant composition throughout.
- they are mixed together.
2, heterogeneous mixtures have visibly different substance or phase.
- does not mix
what can you do when balancing a chemical equation
only change the number in front of the R and P – coefficients.
H2O -> 2 H2O
% Atom economy (equation )
% Atom economy = molar mass of the desired P / molar mass of all reactants x 100.
100 - the %AE = wasted reactants
what is the unit of mole
mol
state 2 equations to calculate moles
1, mol = mass/molar mass (n=m/M)
2, mol = concentration x volume (n=cV)
V must be in dm^3
definition of mole
it is the SI unit for amount of substance (n),
1 mol = 6.02 x10^23 elementary entities.
the number of Cl molecules and Cl atoms in 1.00 mol of Cl gas, Cl2.
- 6.02 x 10^23 molecules of Cl2
- 6.02 x 10^23 2x6.02 x 10^23 = 1.2x10^24 Cl atoms
state the definition of relative atomic mass (Ar)
is the weighted average mass of the naturally occurring isotopes of an element relative to 1/12 the mass of an atom of C-12.
- find on PT
- eg. H = 1.01
definition of AMU
Atomic mass unite, which has a mass of 1.66 x 10^-27
calculating relative atomic mass (Ar)
Ar = (relative abundance x mass of the isotope) +()+() / 100
state the definition of relative molecular mass (Mr)
Is the weighted average mass of a molecule relative to 1/12 the mass of an atom of C-12.
- is the sum of the Ar of the atoms in the molecule.
- eg, H2O = 2x H (1.01)
1 xO (16)
16 + 2x1.01 = 18.02
the unit of Molar mass
g mol^-1
Molar mass definition (M)
Is the mass in grams of one mole of a substance.
- one mole of substance contain 6.02 x 10^23 particles.
- numerically = relative atomic mass.
Molar mass for molecules
The the sum of all (number of the atoms in the molecule x its Ar) = Mr of the molecule = M
converting between cm^3 and dm^3
10^-3
1cm^3 x 1dm^3/1000cm^3 = 0.001dm^3
where and what is Molar ratio
the Coefficients in the balanced equation tells the mol of R and P
2A + 3B -> C + 2D
2 mol of A react with 3 mol of B to form C and 2 mol of D
- one reactant is limiting and one is excess.
