USING ENGLISH FOR CALCULATE

stoichiometry

Stoikiometri is a science that studies and quantifies quantitative relationships of reactants and products in chemical reactions (chemical equations).

A. Basic Law of Chemistry

1. Understanding Basic Law of Chemistry

The basic law of chemistry is the basic law governing the mechanism of the occurrence of a chemical reaction involving reactants and products.

2. Basic Chemical Laws

The basic law of chemistry consists of 5 basic laws such as mass conservation law, fixed comparison law, multiple comparison law, volume comparison law and avogadro law.

B. Mr. and Ar

A. Understanding Relative Atomic Mass (Ar)

The relative atomic mass is the average mass of an atom divided by the mass of the reference atom C-12 atoms.
Sample Problem: An atom X has an average mass of 12 x 10> -23 gr. If 1 C-12 atom has a mass of 2 x 10> -23, then find Ar of the X atom!

B. Relative Molecular Mass (Mr)
The relative molecular mass is the average mass of the molecule divided by the mass of the reference atom C-12 atoms.
Sample Problem: A molecule X has an average mass of 14 x 10> -23 gr. If 1 C-12 atom has a mass of 2 x 10> -23, then find Mr. from the X molecule!

C. Empirical Formulas and Molecular Formulas

Molecular formula is a formula that states the number and type of atoms that make up a compound, While the empirical formula is not much different from the formula molecule, because both show the number and type of atoms that make up a compound, the difference in this empirical formula comparison of the number of atoms simplified as small as possible.

D. Limiting reagents

Limiting reagent is an element / compound that reacts with other substances / compounds to form a product.

E. Hydrate Compounds

Hydrate compounds are one of the chemical compounds that molecules bind to water molecules.

F. The Concept of Mol

Mol is the number of substances of an element that contains some form of elements such as atoms, molecules, ions or electrons. Here is the relationship of mole with several categories including:

1. The Mole Relation With The Number Of Particles

    Mol is the number of substances of an element that contains some form of elements such as atoms, molecules, ions or electrons. Then what is the relationship between the mole and the number of particles? Chemical scientists agree and agree that 1 mole of an element contains 6.02 × 1023 particles of atoms of that element, whereas 1 mole of a compound contains 6.02 × 1023 molecular particles of the compound.

for example :

In a gas cylinder, there is a 3.01 x 1023 particles of Cl2 gas atoms, compute the mol of Cl2 gas contained in the gas cylinder !!

2. Relationship of Mol With Mass

To determine the moles of an element / compound that only the mass know it, then the formula that we can use is as follows:

for example :

Yodhia has 128 grams of pure copper, then determine the mole of copper held by Yodhia!

3. Relation of Mol With Volume

    The mole relationship sub subject to this volume only applies to the gas compound / element. So after we find the mole of the gas, then our next step is to find the volume of the gas.

The process of finding the volume of a gas can be written in the following two phases:

Finding Moles From An Element / Compound in the Gas → Finding the Volume From the Gas (STP / Non STP)

To find the moles of an element / gas known compound, the formula we use is the following formula:

While to find the mole and volume of an element / compound in the form of gas that is not known massnya, then we use the formula there are 2 namely:

1. In Standard Condition (STP) Temperature 0 C and pressure 1 Atm

    V=n/22,4

2. In Non-Standard State Temperature n C and Atm N Pressure

   P.V=n.R.T

In the non-STP state, the value of n for temperature and pressure can vary, in standard state (STP) state, the temperature and pressure values can not be changed (absolute at 0 ° C and 1 μm pressure).

for example :

In a gas cylinder with 0 C temperature and 1 atm pressure, there is 44 g of CO2 gas, then determine the volume of CO2 gas contained in the gas cylinder!

First let us first determine the moles of the CO2 gas. Known mass of CO2 gas that is equal to 44 gr, then molnya:

N = gr / Mr

Then 44/44 = 1 mol

                                                 

Secondly, we find the volume by using the formula:

       V = n x 22.4

Then = 1 x 22.4 = 22.4 Liters of CO2 Gas

Thus, there are 22.4 liters of CO2 gas in the gas cylinder.