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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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