Inorganic Chemistry Answers

1. A gram of soil sample as received contains 15.00% water. After oven drying to remove the mixture, it was found to contain 16.00% K. Find the %K in the original sample as received. 

1. A groundwater at pH 7.5 is in equilibrium with P_C02 = 10^-1•5 atm and with siderite (FeC0₃(s)). Determine the total dissolved Fe concentration.

1. In some water softening operations, Mg²⁺ must be removed from solution along with Ca²⁺. What pH is required to lower TOT Mg to 10 mg/L as CaC0₃ by precipitation of Mg(OH)₂(s)?

3. Nuclear chemistry

1. Calculate the binding energy per nucleon in MeV for the iron isotope with an atomic number of 26 and a mass number of 56, 56Fe26 which has an atomic mass of 55.9349 amu.

2. Calculate:

a. The rate constant for the radioactive disintegration of cobalt-60, an isotope used in cancer therapy. 60Co27 decays with a half-life of 5.2 years to produce 60Ni28.

b. The fraction and the percentage of a sample of the 60Co27 isotope that will remain

after 15 years.

c. How long it takes for a sample of 60Co27 to disintegrate to the extent that only 2 % of the original amount remains?

d. The half-life of 216Po84 is 0.16 s. How long does it take to reduce a sample of it to the negligible amount of 0.000010 % of the original amount (1.0 x 10-7 times the original amount)?

2. Oxidation-Reduction reactions

1. Iron (II) is oxidised to iron (III) by chlorine. Use the half reaction method to balance the equation for the reaction: Fe2+ + Cl2 → Fe3+ + Cl- 2. The dichromate ion oxidizes iron (II) to iron (III) in acid solution. Balance the equation:

Cr2O 2-

+ H3O+

+ Fe2+

→ Cr3+

+ Fe3+

+ H2O, by the half-reaction method

1. Acids and Bases

1. What is the pH of a solution of HCl with a concentration of 1.2 X 10-3 M?

2. The pH of a 0.0516 M solution of nitrous acid, HNO2, is 2.34. What is its Ka?

From periodic table explain the following; Cl‐1, Li 1, Mg +2, S6, Cs +1, Al +3, O -2 and Ca +2

Lead metal is obtained from lead sulfide through the following reaction:

2PbS(s) + 2C(s) + 3O₂(g) → 2Pb(s) +2CO(g) + 2SO₂(g)

(a)If 100g of PbS is reacted with excess C and O_2, calculate the mass of lead metal obtained. ( 5 )

(b)Suppose 100 g of PbS is reacted with 4g of C and 20g O₂.

Find the limiting reactant for this reaction.

( 4 )

(c)For question (b) above, calculate the mass of lead metal obtained. ( 4 )

(d)By referring to the question (c) above, If 31.2g Pb is obtained as the yield. Calculate the percentage of yield. ( 2 )

(e)Calculate mass of oxygen is needed to produce 500g of lead metal.

1. Calculate the amount of heat required to raise the temperature of 7.25g of liquid water from 22.7^oC to 29.2^oC.
2. Calculate the amount of heat required to evaporate 5.20g of liquid water
3. Calculate the amount of heat to be released when 6.50g of water vapor condenses.
4. What phenomenon is responsible for the maximum temperature at the boundary of the stratosphere and the atmosphere?
5. What function does a third body serve in an atmospheric chemical reaction?
6. Why does the lower boundary of the ionosphere lift at night?

Using the appropriate gas laws, calculate the quantities denoted by the blanks below.

Conditions before Conditions after

n₁, mol V₁, L P₁, atm T₁, K n₂, mol V₂, L P₂, atm T₂, K

1.25 13.2 1.27 298 1.25 (a)___ 0.987 298

1.25 13.2 1.27 298 1.25 (b)___ 1.27 407

1.25 13.2 1.27 298 4.00 (c)___ 1.27 298

1.25 13.2 1.27 298 1.36 (d)___ 1.06 372

1.25 13.2 1.27 298 1.25 30.5 (e)___ 298