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# 7 problems in Chemistry

#1 You dissolve 12.6352 g of potassium iodide in water and bring the volume of solution to 250.0 ml. What is the molar concentration of KI?

#2 What volume of 0.0436 molar hydrochloric acid is required to react with 30.0 ml of 0.0278 molar LiOH?

#3 An AM radio station broadcasts using electromagnetic radiation at 1490 kilohertz. What is the wave length of this radiation in meters?

#4 Using the Bohr equation for the hydrogen atom calculate the ionization energy for hydrogen.

#5 Give the electron configuration of each of the following atoms using the inert gas notation. (a) K (b) Mn

#6 Give the set of four quantum numbers that describe the last electron to be placed in the electron configuration of the following atoms. (a) Xe (b) Si

#7 Write the ionic equations for the following reactions in aqueous solution.
(all numbers are small)
a. HNO3 (aq) + KOH (aq) ---> KNO3 (aq) + H2O (1)

B. BaCL2 (aq) + Na2SO4 (Aq) --> BaSO4 (s) + 2 NaCL (aq)

#### Solution Preview

The key concept in all these problems is to understand the relationship between molar concentration, volume and number of mole.
Molar concentration is calculated by:
Molar Concentration(M)=Number of mole(mol)/Volume(L)

1. You dissolve 12.6352 g of potassium iodide in water and bring the volume of solution to 250.0 ml. What is the molar concentration of KI?
Molecular weight of KI=39 + 127 = 166 (g) (from periodic table)
Number of mole of KI =12.6352/166=0.076 (mol)
Hence molar concentration =0.076/0.25=0.3(M)

2. What volume of 0.0436 molar hydrochloric acid is required to react with 30.0 ml of 0.0278 molar LiOH?
Write the reaction:
HCl + LiOH = LiCl + H2O
Hence 1 mole of HCl will react with 1 mole of LiOH
Number of mole of LiOH available for reaction ...

#### Solution Summary

The solution provides detailed explanations and calculations for different concepts in general chemistry such as molar concentration, ionization energy and electron configuration.

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