1. Lecture 5: Chemical Quantities and reactions
Chemistry - SPRING 2017
Course lecturer :
Jasmin Šutković
20th March 2017

2. Contents The mole Molar Mass and Calculations
International University of Sarajevo
The mole
Molar Mass and Calculations
Equations and in chemical reactions
Types of chemical reactions
Energy in Chemical reactions

3. Mole
In chemistry, particles such as atoms, molecules, and ions are counted by the mole, which contains 6.02 x1023 items.
This value, known as Avogadro’s number, is a very big number because atoms are so small that it takes an extremely large number of atoms to provide a sufficient amount to weigh and use in chemical reactions.
Avogadro’s number is named for Amedeo Avogadro (1776–1856), an Italian physicist.

4. Avogadro’s number tells us that one mole of a compound contains 6
Avogadro’s number tells us that one mole of a compound contains 6.02 x1023 of the particular type of particles that make up that compound.
1 mole of carbon contains 6.02 x1023 carbon atoms;
1 mole of aluminum contains 6.02 x1023 aluminum atoms;
1 mole of sulfur contains 6.02 x1023 sulfur atoms

5. Atoms(N)= n x Na ( Avogadros No)
Conversion factor
Atoms(N)= n x Na ( Avogadros No)

6. Moles and Elements in a given formula

7. Sample problem

9. Equations in Chemical Reactions
Chemical substance converter into a new substance = chemical change (different formula with different properties)

12. Balancing of Chemical R.
Every chemical reaction must be written as a balanced equation, which shows the same number of atoms for each element in the reactants as well as in the products!
H2 + O2  H2O - unbalanced
2H2 + O2  2H2O - balanced

13. This illustrates the Law of Conservation of Matter, which states that matter cannot be created or destroyed during a chemical reaction.

14. Combination Types of Reactions
In a combination reaction, two or more elements or compounds bond to form one product.
For example, sulfur and oxygen combine to form the product sulfur dioxide.

15. Examples

16. Decomposition Reactions
In a decomposition reaction, a reactant splits into two or more simpler products.
For example, when mercury (II) oxide is heated, the compound breaks apart into mercury atoms and oxygen
2HgO  2Hg + O2

18. Replacement Reactions
In a replacement reaction, elements in a compound are replaced by other elements.
In a single replacement reaction, a reacting element switches place with an element in the other reacting compound

19. Double replacement
In a double replacement reaction, the positive ions in the reacting compounds switch places.
As others have indicated, when a reagent is noted as being aqueous or (aq), that means that it is present as a water solution. If it is labeled a liquid or (l), that means it is present as a pure substance in a molten state. One thing that is important to stress is that anything marked (aq) in a chemical equation brings implied water along with it, which may change how it behaves in a reaction.

20. Combustion reactions

21. Oxidation reactions

22. Redox reactions
In an oxidation–reduction reaction (redox), electrons are transferred from one substance to another. If one substance loses electrons, another substance must gain electrons.
Oxidation is defined as the loss of electrons; reduction is the gain of electrons.

23. Molar relationship in Chemical Reactions
In any chemical reaction, the total amount of matter in the reactants is equal to the total amount of matter in the products.
Thus, the total mass of all the reactants must be equal to the total mass of all the products
Known as the law of conservation of mass, which states that there is no change in the total mass of the substances reacting in a chemical reaction.

27. Mass Calculations m n M

28. Energy in Chemical Reactions
The activation energy is the amount of energy required to break the bonds between atoms of the reactants.
Three Conditions Required for a Reaction to Occur
1. Collision The reactants must collide.
2. Orientation The reactants must align properly to break and form bonds.
3. Energy The collision must provide the energy of activation.

29. In an exothermic reaction ( exo means “out”) the energy of the products is lower than the energy of the reactants. Thus, heat is released in exothermic reactions.
In endothermic reactions ( endo means “within”) the energy of the products is higher than that of the reactants. Thus, heat is absorbed in endothermic reactions.

31. Speed of reaction (amount of reactants used up in chemical reaction).
Rate of reaction
Speed of reaction (amount of reactants used up in chemical reaction).
Factors that influence the speed:
Temperature
Concentration
Catalyst