# Chemical calculations

## Chemical calculations

The following text is used only for teaching, research, scholarship, educational use and informative purpose following the fair use principles.

We thank the authors of the texts and the source web site that give us the opportunity to share their knowledge

# Chemical calculations

Chemical Calculations

Relative atomic mass (Ar): this is the mass of one atom of the element compared with the mass of one atom of Hydrogen

On the relative atomic mass scale the atomic mass of Hydrogen = 1

Use a Periodic table to help you answer these questions.

1. How many times heavier is one atom of Sodium (Na) than one atom of Hydrogen?

1. How many times heavier is one atom of Oxygen (O) than one atom of Hydrogen?
1. How many atoms of Nitrogen (N) are needed to equal the mass of one atom of Iron (Fe)?

Relative formula mass (Mr): this is the mass of all the relative atomic masses of all the atoms in the formula of the compound

Use a periodic table to help you work out the relative formula masses of these compounds. An example has been done to help show you how.

E.g. (NH4)2 CO3               N  x 2  = 14 x 2       = 28
H4  x 2 =(H x 8)               = 1 x 8         =  8
C  x 1                             = 12 x 1        = 12
O x 3                             = 16 x 3       = 48

Total         = 96

1. CO2

1. SO2
1. NaOH

1. KCl

1. Ca(OH)2

1. HNO3

1. CuCO3

1. NH4NO3

1. CuSO4 . 5H2O

1. Mg(HCO3)2

Moles: M - the amount of a substance that contains Avogadros number of particles of the substance is called one mole of substance

The amount of substance in moles = Mass of substance
Mass of 1 mole of substance

E.g. what is the amount of Iron present in 196 g of Iron (Fe)

Ar of Iron = 56

Amount of Iron = Mass of Iron­
Mass of 1 mole of Iron

Amount of Iron = 196g = 3.5 mol
56g

Use a periodic table to work out how much of each substance is present

1. 1 mol of sodium atoms Na

1. 2 mol of bromine molecules Br2

1. 0.25 mol of nitrogen molecules N2

1. 0.5 mol of sulphur atoms S

1. 0.25 mol of sulphur molecules S8

1. Moles of sodium in 46 g of sodium Na

1. Magnesium in 0.6 g of magnesium Mg

1. Oxygen molecules in 32 g of Oxygen O2

1. 1 mol of sulphur dioxide molecules SO2

1. 2 mol of calcium carbonate CaCO3

Reactions in solutions: Molar solutions

A molar solution is a solution containing 1 mole of a substance made up to one liter (1 dm3) of solution.

E.g. A molar solution of sodium hydroxide (NaOH) contains 1 mol of NaOH in 1 dm3 (1000 cm3) of solution.

This is equal to 40g of NaOH (23 + 16 +1) in 1000cm3 of solution
OR
20g of NaOH in 500cm3 of solution
OR
10 g of NaOH in 250cm3 of solution
OR
80 g of NaOH in 2000cm3 of solution

They are all the same … a 1 molar solution

Molarity = number of grams of solute dissolved x 1000 cm3 of solvent
mass of 1 mole of solute x volume of solvent it is dissolved in

E.g. Molarity of 9.8g of Sulphuric acid H2SO4 dissolve in 100cm3 is: -

1 mole of H2SO4 = 2x1 + 1x32 + 16x4 = 98g

9.8g x 1000 cm3 = 1 M
98g x 100 cm3

1. Calculate the molarity of a solution containing 20g of sodium hydroxide (NaOH) dissolved in 200cm3 of solution

1. Calculate the molarity of a solution containing 126 g of nitric acid (HNO3) dissolved in 500cm3

Concentration is measured in moles per liter = amount of solute in moles
volume of solution in liters

Calculate the concentration of a solution that was made by dissolving 60g of sodium hydroxide (NaOH) and making the solution up to 1 liter

Mass of 1 mole of NaOH = 23 + 16 + 1 = 40g/mol

Amount in moles of sodium hydroxide = 60g    = 1.5 mol
40g/mol
Volume of solution = 1 liter

Amount of mols/volume in liters = 1.5 mol/ liter

Calculate the concentration of the following solutions:

1. 5.6g of potassium hydroxide (KOH) in 500cm3 of solution

2. 7.3 g of hydrogen chloride (HCl) in 250 cm3 of solution

Find the amount of solute dissolved in the following solutions:

1. 250 cm3 of a solution of sodium hydroxide of concentration 2.0 mol/liter

1. 500 cm3 of a solution of Sulphuric acid of concentration 0.12 mol/liter

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.

### Chemical calculations

#### Chemical calculations

Main page Alimentation - nutrition Animals Architecture Art Astrology, esoteric, parapsychology and fantasy Astronomy Biology and genetics Botany and agriculture Chemistry Courses, training, guides, handbooks and tips Culture General and actuality Dermatology, health and wellness Dictionaries and glossaries Economics and finance Education and pediatrics Engineering and technology English grammar and anthology Fashion and show business Fitness Food, recipes and drink Games, play space Geography, geology and environment History Informatics and computer world Jobs world Languages Leisure and DIY do it yourself Lessons for students Literature, biographies and journalism Mathematics, geometry and statistical Medicine Music Notes and concept maps Philosophy Photography and images - pictures chemistry Physiology Psychology and psychoanalysis Quiz questions and answers Religions Rights law and political science Science Sociology and cultural anthropology Sport Summaries and reviews Television, film - movies and comics Theater and communications Theses, themes and dissertations Travel and tourist guides Useful documents and tables Utility, calculators and converters Weather and meteorology

#### Chemical calculations

This is the right place where find the answers to your questions like :

What is Chemical calculations? What does Chemical calculations mean ? Which is the meaning of Chemical calculations?

##### Chemical calculations chemistry notes

Alanpedia.com from 1998 year by year new sites and innovations