The Easiest Way to Understand Chemistry. Chemistry Concepts, Problems and Solutions
Sergey D Skudaev
If you are a parent struggling to help your child with chemistry homework, this is a short book that will help you. It covers key chemistry topics: Oxides, Bases, Acids, Salts, Equivalent proportions, Acid Base reactions, Weight and Volume problems, Equilibrium, Le Chatelier’s Principle, Freezing and Boiling points, Balance Redox Reactions, Stoichiometry (with answers and solutions).If you are student, read this book and you will prove to yourself that you can understand chemistry!
The Easiest Way to Understand Chemistry
Chemistry Concepts, Problems and Solutions
Sergey D Skudaev
© Sergey D Skudaev, 2018
ISBNВ 978-5-4490-9080-5
Created with Ridero smart publishing system
Introduction
My grandma used toВ bake cakes.
ToВ bake aВ cake for five people you have toВ mix:
1В cup ofВ flour
3В eggs
1/2В cup ofВ sugar
100В grams ofВ butter
There was no such thing as aВ fat free cakes at that time. That is why they tasted so good.:)
What if you need toВ bake aВ cake for 20В people? She had the common sense toВ calculate proportions.
20В is 4В times greater thanВ 5.
So, you have toВ use 4В times the number ofВ cups ofВ flour, 4В times as many number eggs and so on. As aВ result, you will have aВ new recipe.
1В * 4=4В cups ofВ flour
3В * 4=12В eggs
1/2В * 4В = 2В cups ofВ sugar
100В * 4В = 400В grams ofВ butter.
InВ the same way you can solve aВ problem about aВ chemical reaction.
All chemical reactions occur inВ equivalent proportions.
If 10В grams ofВ Na2CO3 react with CaCL 2В how many grams ofВ CaCO3 is produced?
10g?В g
1. Na2CO3 + CaCL2 = CaCO3 +2NaCL
All compounds react with each other inВ certain proportions InВ aВ given reaction one mole ofВ Na2CO3 produces one mole ofВ CaCO3.
Mole is molecular mass (MW) inВ grams.
Atomic mass ofВ Na =В 23
Atomic mass ofВ C =В 12
Atomic mass ofВ OВ =В 16
For Na2CO3 the MW is 23 *2 +12 +16*3 = 106 g. – 1 mole
For CaCO3 the MW is 40В +12В +48В = 100g. 1В mole.
106В g Na2CO3 produces 100g CaCO3
10В g Na2CO3 produces X g CaCO3
ToВ calculate X, multiply the matched up values on the opposite ends ofВ the diagonal and divide the product byВ the unmatched value as shown inВ the figure below.
X=10В * 100В / 106В = 9.4В g ofВ CaCO3
Now you have not only solved the chemical equation problem, but also proved toВ yourself that you can understand chemistry.
The Periodic table
InВ 1869, aВ Russian chemist Dmitry Mendeleev published an article inВ which he presented his periodic table ofВ chemical elements. He noticed aВ repetition ofВ physical and chemical properties ofВ chemical elements when he arranged them inВ order ofВ their atomic weight.
Later, it was proved that physical and chemical properties ofВ elements depending on their number ofВ protons and since the number ofВ protons determines an elementМЃs atomic weight, the elements could be arranged inВ order ofВ their atomic weight.
AВ two dimensional periodic table has vertical groups and horizontal periods.
Elements that belong toВ the same group have similar properties. For example, Sodium (Na) and Potassium (K) are alkaline metals that belong toВ the first group. These metals are so soft that they can be cut with aВ knife. When aВ small bit ofВ sodium is placed inВ water, it starts dissolving and producing aВ colorless and odorless gas. This gas is hydrogen.
InВ reaction with water, alkaline metals produce alkali, aВ strong base. Sodium and water produce Sodium hydroxide. (NaOH)
Sodium belongs toВ the first group and the third period.
InВ the 7th group ofВ the same period we find chlorine Cl. Chlorine is aВ greenish poisonous gas that was used as aВ chemical weapon inВ WWI. The reaction ofВ mixing chlorine with water produces aВ strong hydrochloric acid (HCl)
If you mix sodium hydroxide and hydrochloric acid aВ table salt will be produce