Coal has 5 % impurities of lime, 6 % impurities of sand, and 7 % impurities of p

Question

Coal has 5 % impurities of lime, 6 % impurities of sand, and 7 % impurities of pyrite. Calculate volume of gases at 200 degree C and pressure 750 mmHg formed after burning 1 kg of this coal. Products of pyrite combustion are ferric oxide and sulfur dioxide. Write mass percent composition of ash. Gaseous H_2 S can be absorbed by potassium permanganate solution. Balance red-ox reaction of this compound with potassium permanganate in aquatic solution. H_2 S(g) + MnO_4^- (aq) rightarrow SO_4^2- (aq) + Mn^2+ (qq) Colorless Deep purple Colorless Pale pink What purpose of this reaction can be? Shape memory alloy Nitinol has composition 50 atomic percent of nickel and 50 atomic percent of titanium. Calculate masses nickel and titanium needed to prepare 1 kg of this alloy, and volume of hydrogen (STP) evaluated during dissolution this amount in sulfuric acid. 7. Calculate final temperature of system when 100g of iron with temperature 200 degree C inserted in 0.5L of water at the room temperature. Acetone CH_3 COCH_3 was spilled and evaporated in the room. In 25 seconds

Explanation / Answer

5. Balancing the equation,

Ist half-reaction,

MnO4- --> Mn2+

balance O and H,

MnO4- + 8H+ --> Mn2+ + 4H2O

add e-,

MnO4- + 8H+ + 5e- --> Mn2+ + 4H2O

IInd half-reaction,

H2S --> SO4^2-

balance O and H,

H2S + 4H2O --> SO4^2- + 10H+

add e-,

H2S + 4H2O --> SO4^2- + 10H+ + 8e-

multiply this by 5 and Ist half-reaction with 8 and add them together

8MnO4- + 64H+ + 40e- --> 8Mn2+ + 24H2O

5H2S + 20H2O --> 5SO4^2- + 50H+ + 40e-

------------------------------------------------------------------

8MnO4- + 5H2S + 14H+ --> 8Mn2+ + 5SO4^2- + 4H2O

Is balanced

here, H2S is more toxic which is converted to non-toxic SO4^2-.

6. To prepare 1 kg alloy with 50 atomic percent each of Ni and Ti

mass of Ni needed = x g

0.5[(x g x 6.023 x 10^23/58.69)) + ((1000-x) g x 6.023 x 10^23/47.87))] = (x g x 6.023 x 10^23/58.69)

5.13 x 10^21x + 6.3 x 10^24 - 6.3 x 10^21x = 1.03 x 10^22x

x = 549.26 g

So,

Mass of Ti = 1000 - 549.26 = 450.74 g

7. Let Tf be final temperature

Room temperature be 25 oC

heat lost by iron = heat gained by water

heat = mCpdT

density of water = 1 g/ml

volume of water = mass of water

100 x 0.444 (200 - Tf) = 500 x 4.184 (Tf - 25)

8880 - 44.4Tf = 2092Tf - 52300

Tf = 28.64 oC

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