Writing Ionic Equations:
An ionic equation is a simplified chemical equation that shows the reactions of ionic compounds in water.
Ionic compounds are those compounds, which are soluble in water.
Inorder to write an ionic equation:
- Write the balanced chemical equation of the reaction. Include the state symbols.
- Identify ionic compounds that are soluble in water. These compounds become ions in H20. Rewrite the chemical equation in terms of ions.
- Cancel out the spectator ions (Common).
- Write the ionic equation.
Relative Atomic Mass (Ar):
The mass of an atom compared with the Carbon – 12 atom is called its relative atomic mass.
The mass of one mole of atoms is its “relative atomic mass” in grams.
Relative Molecular Mass (Mr):
The mass of a substance made of molecules is known as Relative Molecular Mass.
Hydrogen has (1*2) = 2 and H20 has relative molecular mass of (1*2) + 16 = 18
Relative Formula Mass (Mr):
The mass of a substance made of ions is known as relative formula mass. Ammonia (NH3) has Mr of (1*14) + (3*1) = 58.5.
A mole of a substance is the amount that contains the same number of units as the number of Carbon atoms in 12 grams of carbon-12.
Number of Particles in one mole = 6.02 * 1023
Percentage Compostition of Compounds:
Percentage by mass of an element in a compound
Percentage of Hydrogen in Hydrogen Per Oxide:
Water in Coppoer(II) Sulphate:
Emperical Formula of a compound shows:
- Types of elements present in it.
- Simplest Ratio of the different types of atoms in it.
Inorder to Find the Emperical Formula of a compound:
- Write down the each percentage/ mass separately.
- Divide each by their Mr.
- Now divide all of them with one which has the lowest ratio.
- If any one of the answer is in the decimal form, multiply both with any number (lowest) to get make it a whole number
A compound has 40% Carbon 6.6% Hydrogen & 53.3% Oxygen. Calculate the Emperical Formula of the compound.
C H O
40 6.6 53.3
40/12 6.6/1 53.3/16
3.33 6.6 3.33
3.33/3.33 6.6/3.33 3.33/3.33
1 2 1
Emperical Formula: CH2O
E.g 2 O.72g of Mg combines with 0.28g of Nitrogen. Find its Emperical Formula.
1.5 * 2 1 * 2
Emperical Formula :Mg3N2
The molecular formula shows the actual number of atoms that combine to form a molecule.
To Find the molecular Formula:
- Calculatefor the compound. This gives the number n.
- Multiply the numbers in the empirical formula n.
E.g. Emperical Formula = HO
Relative Molecular Mass = 34
(H = 1 , O = 16) . Find Molecular Formula?
34/17 = 2
HO * 2 = H202
Calculating The Volume of Gas:
1 Mole of every substance occupies 24dm3.
The Concentration of a solution, is the amount of solute in grams or noles, that is dissolved in 1 dm3 of solution.
Yeild is the amount of product, obtained from a reaction.
It is the amount collected at the end of a chemical reaction. The actual yield is always less than the theoretical yield. It is also known as the Practical Yeild.
It is the calculated yield of the amount of prosuct by using stoichiometry. In this Yeild 100% reactants are converted to products, with no losses.
Percentage Purity indicates the amount od pure substance present in a sample of chemical substance.