Simple Mole Concept Notes

• A mole is defined as the amount of substance which contains equal number of particles (atoms / molecules / ions) as there are atoms in exactly 12.000g of carbon-12.

• One mole of carbon-12 atom has a mass of exactly 12.000 grams and contains 6.02 x 10²³ atoms.

The value 6.02 x 10²³ is known as Avogadro Constant.   

 N_A = 6.02 x 10²³ mol^-1

Example:

Calculate the number H atom in 1 mole of NH3.

Simple Mole Concept of Gases Notes

• Molar volume of any gas at STP = 22.4 dm³ mol^-1

• 1 mole of gas has a volume of 22.4 dm³ at s.t.p.
• At s.t.p, volume of gas (dm³) = number of mole X 22.4 dm³ mol^-1
• 1 mole of gas has a volume of 24.0 dm³ at room temperature.
• At room temperature, volume of gas (dm³) = number of mole X 24.0 dm³ mol^-1

Calculate the number of bromide ions in 2 moles of CaBr2

Acids and Bases Quiz

• Define acid and base according to the Arrhenius concept. Give an example for your answer.
• Define the term conjugate acid-base pair.
• Define amphiprotic species.
• Define an acid and a base according to the Brønsted–Lowry concept. Give an acid–base equation and identify each species as an acid or a base.
• What is meant by the conjugate acid of a base?
• Write an equation in which H₂PO₃ acts as an acid and another in which it acts as a base.
• Define an acid and a base according to the Lewis concept. Give a chemical equation to illustrate.
• Explain why an acid–base reaction favors the weaker acid.
• Give two important factors that determine the strength of an acid. How does an increase in each factor affect the acid strength?
• Define autoionization. Write the expression for Kw. What is its value at 25˚C?
• What is meant by the pH of a solution? Describe two ways of measuring pH.
• Which is more acidic, a solution having a pH of 4 or one having a pH of 5?
• Identify the relationship between the strength of an acid and that of its conjugate base.
• Identify the rules for determining the relative strengths of oxoacids.
• Identify the relative acid strengths of a polyprotic acid and its anions.

Explain the difference between orbit and orbital.

• Orbital refers to the volume in space around the nucleus where the probability of finding a particular electron in ˃ 95%.
• Orbit refers to the fixed circular path around the nucleus where a particular electron revolves.

Explain the difference between relative isotopic mass and relative atomic mass of a particular element.

• Relative isotopic mass is the mass of one atom of a particular isotope of the element. 
• Relative atomic mass is the average mass of all the isotopes present in a sample of naturally occurring element.

When moving across the periodic table from Li to Be to B, the first ionization energy increases from Li to Be, then drops for B. The first ionization energy of B is greater than that of Li. Explain why.

• When moving across a period on the periodic table, the value of the effective nuclear charge increases with atomic number. This causes a general increase from Li to Be to B. 
• The even higher value of Be (greater than B) is due to the increased stability of the electron configuration of Be. 
• Beryllium has a filled s-subshell. Filled subshells have an increased stability, and additional energy is required to pull an electron away.