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13 Dec 2019

Al2(SO4)3 + 3Ca(OH)2 â 2Al(OH)3 + 3Ca+2 + 3SO4-2

1. Assuming that the concentration of calcium in the water is 80 mg/L (as Ca), how many mg/L of quick lime (CaO) would be needed to reduce the calcium concentration to 35 mg/L. Also assume that the reaction (conventional lime softening) is stoichiometric, that there is no excess CO2 present that needs to be removed (alum is not added as a coagulant), and that no magnesium will be removed. (Hint: all of the calcium hardness is carbonate hardness.) Atomic weights: Ca=40; O=16; C=12; H=1

2. What is the annual cost of chlorine when the plant is operated at the design flow rate of 20 MGD? Assume that the chlorine is added as a solution of sodium hypochlorite (NaOCl) having a strength of 120 g/L as Cl2, that the dosage is 5 mg/L as Cl2, and that the cost of the solution is $1.75 per gallon.

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Hubert KochLv2

17 Dec 2019

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The simplest method of removing iron from sulphuric acid leach solutions (iron is a common impurity element in all hydrometallurgical processes that needs to be removed and disposed in specially designed tailings ponds) is by neutralization with lime (CaO) to cause its precipitation in the form of ferric hydroxide (Fe(OH)3) at ambient temperature or in the form of goethite (FeOOH) at elevated temperatures (near the boiling point of water). [Of course iron may be precipitated/removed also in the form of jarosite (a complex salt NaFe3(SO4)2(OH)6 ) or hematite (Fe2O3) but these processes are not considered in this problem]. Lime (CaO) plays two roles: first it acts as base by its quick conversion to Ca(OH)2 upon mixing with water (this is called slaking)

CaO (s) + H2O = Ca(OH)2
hence helps to raise the pH by neutralizing the acid; and second by forming gypsum
(CaSO4 ..2H2O (s) ) which is an insoluble compound thus helping to remove excess sulphate from the solution.

You are asked
(a) to write all reactions involved in the neutralization with lime of a 9.8 g/L H2SO4 solution

containing 5.6 g/L Fe3+ (as Fe2(SO4)3);
(b) to calculate the moles of gypsum and Fe(OH)3 will be produced if 100% of the acid and

iron contained in 100 m3 solution are made to react with lime.

WHICH OF THE FOLLOWING IS NOT AN ARRHENIUS BASE? KOH NH3 LiOH Sr(OH)2 Mg(OH)2 WHICH OF THE FOLLOWING IS A STRONG ACID IN AQUEOUS SOLUTION? HC2H3O2 HC1 HC1O2 H2S HC1O WHICH OF THE FOLLOWING REACTIONS IS NOT AN ACID-BASE REACTION? CaO + SiO2 rightarrow CaSiO3 CH3CHO + H2 rightarrow CH3CH2OH PO4^3- + H2O rightarrow HPO4^2- + OH- Na2O + SO3 rightarrow Na2SO4 BF3 + NH3 rightarrow F3BNH3 ALL OF THE FOLLOWING ARE OXIDATION-REDUCTION REACTIONS EXCEPT: H2(G) + F2 rightarrow 2HF(G) Ca(S) + H2(G) rightarrow CAH2(S) 2K(S) + 2H2O(L) rightarrow 2KOH(AQ) H2(G) 6Li(S) + N2(G) rightarrow 2Li3N(S) Mg3N2(S) + 6H2O(L) rightarrow 3Mg(OH)2(S) + 2NH3(G) WHICH OF THE FOLLOWING IS BEST DESCRIBED AS AN OXIDATION-REDUCTION REACTION? SO2(G) + H20(L) rightarrow H2SO3(AQ) 2C1(G) rightarrow C12(G) 3O2(G) rightarrow 2O3(G) 2NO2(G) rightarrow N2O4(G) SO2(G) + O2(G) rightarrow SO3 WHICH OF THE FOLLOWING REACTIONS INVOLVES NEITHER OXIDATION NOR REDUCTION? N2 + 3H2 rightarrow 2NH3 NH4NO2 rightarrow N2 + 2H2O Cu + 2Ag+ rightarrow Cu^2+ + 2Ag 2CrO4^2- + 2H+ rightarrow Cr2O7^2- + H20 C2H4 + H2 rightarrow C2H6 ASSIGN OXIDATION NUMBERS TO EACH ATOM IN NITROUS ACID. H = +1, N=+5, 0=-l H=+l, N=+5, O=-2 H=+l, N=+3, O=-l H=+l, N=+3, O=0 H=+l, N=+3, O=-2 FOR THE REACTION THAT OCCURS IN A LEAD STORAGE BATTERY, Pb(S) + Pb02(S) + 2H+(AQ) + 2HS04-(AQ) rightarrow 2PbSO4(S) + 2H20(L) THE OXIDIZING AGENT IS HSO4- PbSO4 Pb PbO2 H+ IN THE BALANCED EQUATION 3Na+ + 3OH- + P4 + 2H2O rightarrow 3Na+ + 3H2OP2- + PH3 WHAT IS THE REDUCING AGENT? OH- Na+ H2O P4 PH3 ALL OF THE FOLLOWING REACTIONS ARE CALLED COMBINATION REACTIONS EXCEPT BaO(S) + SO2(G) rightarrow BaSO3(S) C6H10(L) + Br2(L) rightarrow C6H10Br2(L) Br2(L) + H20(L) rightarrow HOBr(AQ) + HBr(AQ) CaC12(S) + 6H2O(L) rightarrow CaC12 * 6H2O(S) 3H2(G) + N2(G) rightarrow 2NH3(G) A 12.0 SAMPLE OF NaOH IS DISSOLVED IN WATER, AND THE SOLUTION IS DILUTED TO GIVE A FINAL VOLUME OF 1.80 L. THE MOLARITY OF THE FINAL SOLUTION IS 6.67 M 0.167 M 0.300 M 0.150 M 1.85 M HOW MANY GRAMS OF LITHIUM NITRATE, LiN03 (68.9 G/MOL), ARE REQUIRED TO PREPARE 511.5 mL OF A 0.101 M LiN03 SOLUTION? 0.000750 G 3.56 G 0.281 G 349 G 0.0735 G WHICH SUBSTANCE WOULD PRODUCE 2 MOL OF PARTICLES PER MOLE OF SOLUTE WHEN DISSOLVED IN WATER? NH4CH3COO CH2O CO2 SO2 A1(NO3)3 WHAT MASS OF H3PO4 (98 G/MOL) IS PRESENT IN 59.7 L OF A 0.0438 M SOLUTION OF H3P)4? 0.0267 G 0.00390 G 2.56 Times 10^2 G 1.34 Times 10^5 G 13.9 G WHICH OF THE FOLLOWING IS A CORRECT STATEMENT OF CHARLE'S LAW, V/T = k THE VOLUME OF A GAS VARIES PROPORTIONALLY WITH THE PRESSURE THE VOLUME OF A GAS SAMPLE VARIES DIRECTLY WITH THE ABSOLUTE TEMPERATURE ALL GAS SAMPLES OF THE SAME VOLUME OF STP CONTAIN THE SAME NUMBER OF ATOMS THE PRESSURE OF A GAS SAMPLE VARIES INVERSELY WITH THE VOLUME. ALL GAS SAMPLES OF THE SAME VOLUME AT STP CONTAIN THE SAME NUMBER OF MOLECULES. THE DENSITY OF A GAS IS 3.48 G/L AT STP. WHAT IS ITS MOLAR MASS? 115.7 G/MOL 104.7 G/MOL 6.4 G/MOL 22.4 G/MOL 78.0 G/MOL WHAT VOLUME OF AMMONIA GAS, MEASURED AT 455.9 MM HG AND 57.4 DEG C, IS REQUIRED TO PRODUCE 2.78 G OF AMMONIUM SULFATE ACCORDING TO THE FOLLOWING BALANCED CHEMICAL EQUATION? 2NH3(G) + H2SO4(AQ) rightarrow (NH4)2SO4(S) 0.0002233 L 0.000931 L 0.476 L 7.38 L 1.90 L CALCIUM NITRATE WILL REACT WITH AMMONIUM CHLORIDE AT SLIGHTLY ELEVATED TEMPERATURES, AS REPRESENTED IN THE EQUATION Ca(NO3)2(S) + 2NH4C1(S) rightarrow 2N2O(G) + CaC12(S) + 4H2O(G) WHAT IS THE MAXIMUM VOLUME OF N20 AT STP THAT COULD BE PRODUCED USING A 2.40-MOL SAMPLE OF EACH REACTANT? 6.55 Times 10^2 L 108 L 1.86 Times 10^-2 L 53.8 L 22.4 L WHAT IS THE PARTIAL PRESSURE OF CARBON DIOXIDE IN A CONTAINER THAT CONTAINS 7.64 MOL OF OXYGEN, 1.68 MOL OF NITROGEN, AND 1.42 MOL OF CARBON DIOXIDE WITH A TOTAL PRESSURE OF 529 MM HP? 376 MMHG 80.6 MMHG 82.7 MMHG 69.9 MMHG 529 MMHG A SAMPLE OF HYDROGEN IS COLLECTED BY WATER DISPLACEMENT AT 23.0 DEG C AND AN ATMOSPHERIC PRESSURE OF 735 MMHG. ITS VOLUME IS 568 ML. AFTER WATER VAPOR IS REMOVED, WHAT VOLUME WOULD THE HYDROGEN OCCUPY AT THE SAME CONDITIONS OF PRESSURE AND TEMPERATRE? (THE VAPOR PRESSURE OF WATER AT 23.0 DEG C IS 21 MMHG)509 mL 539 mL 552 mL 568 mL 585 mL

Balance the following Chemical Equations:

____Fe(s) + ____H₂O(g) Â® ____Fe₃O₄(s) + ____H₂(g)

____C₂H₆(g) + ____O₂(g) Â® ____CO₂(g) + ____H₂O(g)

___ C₆H₁₄ (l) + ___ O₂ (g) Â® ___ CO₂ (g) + ___ H₂O (g)

___ C₃H₈O₃ (l) + ___ O₂ (g) Â® ___ CO₂ (g) + ___ H₂O (l)

___ NaN₃ (s) Â® ___ Na (s) + ___ N₂ (g)

__ C₃H₅N₃O₉ Â® __ CO₂ + ___ N₂ + ___ H₂O + ___ O₂

Write and Balance the equations:

Aqueous calcium hydroxide reacts with aqueous sodium carbonate to produce solid calcium carbonate and aqueous sodium hydroxide.

Solid iron reacts with Oxygen gas to form solid Iron (II) oxide

Copper(II) sulfide is oxidized by molecular oxygen to produce gaseous sulfur trioxide and solid copper(II) oxide. The gaseous product then reacts with liquid water to produce liquid hydrogen sulfate as the only product. Write the two equations which represent these reactions.

Indicate what type, or types, of reaction each of the following represents: (precipitation, acid-base, and oxidation-reduction.)

(A) H₂O(g) + C(s) â¶ CO(g) +H₂(g)

(B) 2KClO₃(s) â¶ 2KCl(s) +3O₂(g)

(D) Pb(NO₃)₂(aq) + H₂SO₄(aq) â¶ PbSO₄(s) + 2HNO₃(aq)

4. Silver can be separated from gold because silver dissolves in nitric acid while gold does not. Is the dissolution of silver in nitric acid an acid-base reaction or an oxidation-reduction reaction? Explain your answer.

5. Determine the oxidation states of the elements in the compounds listed. None of the oxygen-containing compounds are peroxides or superoxides.

(A) H₃PO₄

(B) Al(OH)₃

6. Complete and balance the following acid-base equations:

(A) A solution of HClO₄ is added to a solution of LiOH.

(B) Aqueous H₂SO₄ reacts with NaOH.

7. Write the molecular, total ionic, and net ionic equations for the following reactions:

(A) Ca(OH)₂(aq) + HC₂H₃O₂(aq) â¶

(B) H₃PO₄(aq) + CaCl₂(aq) â¶

8. Write the balanced equation, then calculate the number of moles and the mass of Mg required to react with 5.00 g of HCl and produce MgCl₂ and H₂. Ans: 1.67 g Mg

9. H₂ is produced by the reaction of 118.5 mL of a 0.8775-M solution of H₃PO₄ according to the following equation: 2Cr + 2H₃PO₄ â¶ 3H₂ + 2CrPO₄. How many grams of H₂ are produced? Ans: .315 g H₂

10. Automotive air bags inflate when a sample of sodium azide, NaN₃, is very rapidly decomposed.

2NaN₃(s) â¶ 2Na(s) + 3N₂(g)

What mass of sodium azide is required to produce 2.6 ft³ (73.6 L) of nitrogen gas with a density of 1.25 g/L?

Ans: 142 g NaN₃

11. Urea, CO(NH₂)₂, is manufactured on a large scale for use in producing urea-formaldehyde plastics and as a fertilizer. What is the maximum mass of urea that can be manufactured from the CO₂ produced by combustion of 1.00 x 10⁴ grams of CO₂?

CO₂(g) + 2NH₃(g) â¶ CO(NH₂)₂(s) + H₂O(l)

Ans: 1360 g urea

12. What volume o f 0.750 M hydrochloric acid solution can be prepared from the HCl produced by the reaction of 25.0 g of NaCl with excess sulfuric acid? NaCl(s) + H₂SO₄(l) â¶ HCl(g) + NaHSO₄(s)

Ans: .570 L

13. A sample of 0.53 g of carbon dioxide was obtained by heating 1.31 g of calcium carbonate. What is the percent yield for this reaction? CaCO₃(s)â¶CaO(s) + CO₂(s)

Ans: 92.0 %

14. Citric acid, C₆H₈O₇, a component of jams, jellies, and fruity soft drinks, is prepared industrially via fermentation of sucrose by the mold Aspergillus niger. The equation representing this reaction is

C₁₂H₂₂O₁₁ + H₂O +3O₂ â¶2C₆H₈O ₇+ 4H₂O

What mass of citric acid is produced from the reaction of 150. grams of sucrose if the yield is 92.30%?

Ans: 155 g

15. The phosphorus pentoxide used to produce phosphoric acid for cola soft drinks is prepared by burning phosphorus in oxygen.

(A) What is the limiting reactant when 0.200 mol of P₄ and 0.200 mol of O₂ react according to P₄+5O₂ â¶ P₄O₁₀?

(B) Calculate the percent yield if 10.0 g of P₄O₁₀ is isolated from the reaction.

Ans: 88.0 %

16. What is the limiting reactant when 1.50 g of lithium and 1.50 g of nitrogen combine to form lithium nitride, a component of advanced batteries, according to the following unbalanced equation? Li + N₂ â¶ Li₃N

Ans: Li

17. What is the concentration of NaCl in a solution if titration of 15.00 mL of the solution with 0.2503 M AgNO₃ requires 20.22 mL of the AgNO₃ solution to reach the end point?

AgNO₃(aq) + NaCl(aq) â¶ AgCl(s) +NaNO (aq)

Ans: .3374 M

18. In a common medical laboratory determination of the concentration of free chloride ion in blood serum, a serum sample is titrated with a Hg(NO₃)₂ solution.

2Cl^â(aq) + Hg(NO₃)₂(aq) â¶ 2NO₃^â(aq) + HgCl₂(s)

What is the Cl^â concentration in a 0.25-mL sample of normal serum that requires 1.46 mL of .000825 M Hg(NO₃)₂(aq) to reach the end point?

Ans: 0.009636 M

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