# Help with any of these:    21

Help with any of these:

21. Aluminium sulphate is often used by gardeners to acidify soil and can be produced by the reaction
2Al(OH)3(aq) + 3 H2SO4(aq) à Al2(SO4)3(aq)  + 6 H2O(l)
The volume of 0.275 mol/L H2SO4(aq) needed to react completely with 112 mL of 0.355 mol/l Al(OH)3(aq) is
A. 96.4 mL
B. 145 mL
C. 168 mL
D. 217 mL

22. To produce the anti cancer drug cisplatin (Pt (NH3)2Cl2(s)), a technician reacted NH3(aq) with excess K2PtCl4(aq). The reaction follows
K2PtCl4(aq) + 2 NH3(aq) à Pt(NH3)2Cl2(s) + 2 KCl(aq)
The data was recorded by the technician as follows.
Concentration of NH3(aq) used = 0.450 mol/L
Mass of filter paper = 0.725 g
Mass of filter paper and solid precipitate = 9.544 g
The volume of NH3(aq) used by the technician was
A. 32.7 mL
B. 65.3 mL
C. 131 mL
D. 141 mL

23.  When calcium reacts with nitrogen, calcium nitride is formed, as shown in the following balanced chemical equation:
3 Ca(s) + N2(g)  Ca3N2(s)
If 24.0 g of calcium and 12.0 g of nitrogen are available for this reaction, the limiting reagent is:
A.        calcium
B.        nitrogen
C.        calcium nitride
D.        both calcium and nitrogen will be completely consumed

24.  When 45 mL of 0.25 mol/L sulfuric acid is mixed with 25 mL of 0.48 mol/L calcium hydroxide, the solution
A.        is acidic
B.        is neutral
C.        is basic
D.        not enough information is given

25.  Consider the reaction equation 3 Fe(s) + 4 H2O(l)  Fe3O4(s) + 4 H2(g). If 3.0 mol Fe reacts with 1.0 mol H2O in ideal conditions, which statement is true?
A.        Fe is in excess.
B.        H2O is in excess.
C.        Both reactants are completely consumed.
D.        Not enough information is given to answer the question.
26. A group of students performed a titration analysis. The results are given in the graph below.

The indicator that the students should use to find the endpoint pH is:
A.        methyl orange
B.        methyl red
C.        bromothymol blue
D.        phenolphthalein

27.  In a titration, a 20 mL sample of NaOH(aq) was neutralized by 14.9 mL of 0.13 mol/L H2SO4(aq). The concentration of the base is
A. 8.7 mol/L
B. 0.35 mol/L
C. 0.19 mol/L
D. 0.048 mol/L

28.  For complete neutralization, 15.0 mL of 0.35 mol/L sodium hydroxide solution was required to react with 0.425 g of an acid. The possible identity of the acid is.
A. HBr (aq)
B. HCl(aq)
C. HNO3(aq)
D. H2SO4(aq)

29.  A lab group decides to test a manufacturer’s claim that an antacid product contains 200 mg of sodium bicarbonate. Each tablet was placed into an Erlenmeyer flask, 10.00 mL of water was added, and then the tablets were crushed. An indicator was added to each flask, and then each sample was titrated with 0.200 mol/L hydrochloric acid. The titration evidence was collected in the table below

Titration of 10.00 mL of NaHCO3(aq) with 0.200 mol/L HCl(aq)
Trial
1
2
3
4
11.6
21.7
31.7
41.8
0.6
11.6
21.7
31.7

Indicator colour
red
orange
orange
orange

The calculated mass of sodium bicarbonate in the antacid tablet is:
A.        169 mg
B.        173 mg
C.        84.6 mg
D.        86.5 mg

30.   During a titration, results were recorded for three trials for the complete neutralization of 0.100 mol/L potassium carbonate solution with hydrochloric acid

The Volume of HCl(aq) Required to React With a Given Volume of K2CO3(aq)

Volume (mL)
Trial 1
Trial 2
Trial 3
K2CO3(aq)
20.0
20.0
20.0
HCI(aq)
22.3
22.5
22.4

From the data, it can be calculated that the concentration of the acid is
A. 4.46 X 10–1 mol/L
B. 1.79 X 10–1 mol/L
C. 4.46 X 10–2 mol/L
D. 1.79 X 10–2 mol/L

31.  When a solution of H2S(aq) is mixed with a solution of Pb(NO3)2(aq), the ionic equation of the above reaction is
a.         Pb2+ (aq) + 2NO3–(aq)  Pb(NO3)2(aq)
b.         S2–(aq) + Pb2+ (aq)  PbS(s)
c.         2H+(aq) + S2–(aq) + Pb2+ (aq) + 2NO3–(aq)  PbS(s) + 2H+(aq) + 2NO3–(aq)
d.         S2(aq) + Pb2+ (aq) + 2NO3(aq)  PbS(s) + 2NO3(aq)

32.

In the Haber process, ammonia is formed by the reaction of nitrogen with hydrogen under high pressure and high temperature. The reaction is expressed as follows:

If 2.00 g of N2(g) reacts with excess hydrogen to produce 1.85 g of ammonia, what will the percentage yield be for the reaction?
a.         75.9%  c.         77.9%
b.         76.1%  d.         82.2%

33.  A solution of NaCl(aq) is added dropwise to a 10.0 mL sample of water from an industrial site that contains lead(II) nitrate, Pb(NO3)2(aq). A white precipitate forms immediately. What is the net ionic equation for the reaction that occurred?
A.    Na+(aq) + Cl-(aq) ® NaCl(s)
B.     Pb2+(aq) + 2NO3-(aq) + 2Na+(aq) + 2Cl-(aq) ® PbCl2(s) + 2Na+(aq) + 2Cl-(aq)
C.     Pb2+(aq) + 2NO3-(aq) + 2Na+(aq) + 2Cl-(aq) ® Pb2+(aq) + 2Cl-(aq) + 2NaCl(s)
D.    Pb2+(aq) + 2Cl-(aq) ® PbCl2(s)

NR1  When 12.71 g of copper react with 8.000 g of sulfur, 14.72 g of copper(I) sulphide is produced. What is the percentage yield in this reaction?
2Cu(s) + S(g) ® Cu2S(s)

NR2.   What mass of the reagent in excess will remain after the reaction in which
0.3604 g of H2O(l) react with 0.8000 g of O2(g)?    2H2O(l) + O2(g) ---> 2H2O2

Two suggestions to help.
1. You get help more quickly if you post just one at a time.
2. Most of the problems are either stoichiometric or limiting reagent problems. Here are examples of each; just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html

http://www.jiskha.com/science/chemistry/limiting_reagent_problem.html

The titration problems can be solved by a three step process.
25 mL A + 50 mL of 0.1 B. What is molarity of A.
1. Convert B to mols. mols = M x L = ?
2. Use the coefficients in the balanced equation to convert mols B to mols A.
3. Then M A = mols A/L A.
b.

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