Chemistry Answers

For each redox reaction below, determine the oxidation number of each element present. Write your answer above each symbol for the element.

a. 2Sb(s) + 3I2(g) —> 2SbI3(s)

b. 2Cu2S(s) + 3O2(g) —> 2Cu2O(s) + 2SO2(g)

c. PbO2(s) + Pb(s) + 2H2SO4(aq) —> 2PbSO4(aq) + 2H2O(l)

d. NH4NO3(s) —> 2H2O(g) + N2O(g)

e. Fe2O3(s) + 3CO(g) —> 2Fe(s) + 3CO2(g)

Calculate the standard cell potential for

Zn(s) + Ag*(aa) → Zn²+ + Ag(s)

Assume that all the concentrations are 1.0 M. Standard reduction potentials are given in table 1.

Write half-reactions for each of the following redox reactions. Identify each half-reaction as being either oxidation or reduction. Show your work.

A. SnS2(s) + O2(g) —> SnO2(s) + SO2(g)

B. Mg(s) + N2(g) —> Mg3N2(s)

Balance the following equations, using the oxidization number method for the redox part of the equation. Show your work.

A. Cu2O(s) + H2(g) —> Cu(s) + H2O(l)

B. Cl2(g) + KBr(aq) —> Br2(l) + KCl(aq)

What is the pH of a 1.5x10^-3 M solution of NaOH, a strong base? Show your work.

1.)calculate the volume of 0.400M H3PO4 needed to react with 200.0mL of 0.200 M NaOH

____H3PO4 (aq) +___NaOH(aq) -____Na3PO4(aq) +___H2O(l)

1.)calculate the volume, in mL of 1.72M HCl solution that will react with 2.67 mol of CaCO3? (Ans. 3.10x103mL

___HCl+___CaCO3____CaCl2+___H2O+__CO2

2.)If 0.650% solution of NaCO3 will be used to precipitate Ca+2 from solution, determine the amount of solution, in grams, needed to precipitate 5.00x102mL of 0.01120M Ca+2?(Atomic mass :Na=22.99g/mol:C=12.01g/mol:O=16.00g/mol:Ca=40.08g/mol:Ans.91.3g)

____Na2CO3(aq)+___Ca+2(aq)____CaCO3(s)+___Na+(aq)

3.)calculate the molality of phosphoric acid, H3PO4, in a solution of 29.0g H3PO4 in 250.0g H2O. (atomic mass :H=1.008g/mol:P=30.97g/mol:O=16.00g/mol:Ans.m=1.18mol solute /kg solvent)

4.)Refer to the data given in problem #3, calculate the mole fraction of H3PO4 and H20. (Ans. X H3PO4 =0.979:XH20=0.0209

5.)An aqueous solution has 0.0400g of NaCl (salute) in 2.00kg H2O(solvent). What is the concentration of the solution in parts per million

6.)calculate the volume, in mL, of 1.72M HCl solution that will react with 2.67 mol of CaCO3? (Ans. 3.10x103mL)

__HCl+__CaCl2+__H2O+__CO2

7.)If 0.650% solution of Na2CO3 will be used to precipitate Ca+2 from solution, determine the amount of solution, in grams, needed to precipitate 5.00x102mL of 0.01120M Ca+? (Atomic mass :Na 22.99g/mol:C=12.01g/mol:O=16.00g/mol:Ca=40.08g/mol:Ans.91.3g

___Na2CO3(aq)+__Ca+2(aq)___CaCO3(s)+___Na+(aq)

A storage tank contains 2 moles of Ar, 3 moles of O2, and 5 moles

of N2 at a total pressure of 1000 torr. Calculate partial pressure of

each gas