Sulfur hexafluoride is produced by reacting elemental sulfur with fluorine gas.

Question

Sulfur hexafluoride is produced by reacting elemental sulfur with fluorine gas. S_1 (s) + 24 F_2 (g) rightarrow 8 SF_e (g) What is the percent yield if 18.3 g SF_6 is isolated from the reaction of 10.0 g S_3 and 30.0 g F_2? 40.2% 45.8% 47.6% 61.0% A 1.5991 g sample of a hydrocarbon it combusted to give 1.6918 g of H_2 O and 5.1661 g of CO_21. What is the empirical formula of the compound? CH CH_2 C_2 H_3 C_3 H_4 C_5 H_g How many liters of 0.1107 M KCl (aq) contain 2.50 g of KCl? 0.277 L 0.303 L 3.71 times 10^-3 L 3.30 L 5.94 times 10^-4 L What is the mass of potassium iodide in 50.0 mL of 5.75 times 10^-2 M KI (aq)? 2.88 times 10^-2 g 191 times 10^-1 g

Explanation / Answer

16) as per the balanced equation

one mole (138.1 grams) of salicylic acid will react with one mole of acetic anhydride (102.1 grams) to give one mole of aspirin (180.2 grams)

So, 3.03 grams of salicylic acid will react with = 102.1 X 3.03 / 138.1 grams of acetic anhydride = 2.24 grams

to give = 180.2 X 3.03 / 138.1 grams of aspirin = 3.95 grams of aspirin

Actual yield = 2.04 grams

% yield = actual yield X 100 / theoretical yield = 2.04 X 100 / 3.95 = 51.6%

17) one mole of S8 (256.48 g) will react with 24 moles of F2 ( 24 X 37.99 grams) to give 8moles of SF6 ( 8 X 146.06 grams)

911.76 grams of F2 will react with 256.48grams of S8 to give 1168.48 grams of SF6

1gram of F2 will react with 256.48 / 911.76 grams of S8 to give 1168.48/911.76 grams of SF6

30grams of F2 will react with 30 X 256.48 /911.76 grams of S8 to give = 1168.48 X 30 / 911.76 grams of SF6 = 38.45grams

% yield = 18.3 X 100 / 38.45 = 47.59%

18) We know that the combustion equation for carbon and hdyrogen are

C + O2 --> CO2(g)

1mole of CO2 is obtained from one mole of carbon

So 44grams of CO2 is obtained from 12 grams of carbon

5.1661grams of CO2 must have obtained from = 12 X 5.1661 / 44 grams of carbon = 1.4089 grams carbon

similarly

H2 + 1/2O2 ---> H2O

18grams of H2O obtained from 2 grams of hydrogen

1.6981 grams of H2O will be obtained from 2 X 1.6981 / 18 = 0.18868 grams of hydrogen

Moles of carbon = Mass / atomic weight = 1.4089 / 12 = 0.117

Moles of hydrogen = 0.18868 / 1 = 0.189

Let us divide carbon and hydrogen by 0.117

Carbon = 1 hydrogen = 0.189 / 0.117 = 1.615

Multiply both by 2

so the formula must be C2H3

19) molarity = Moles / volume in litres

Moles = Mass / Molecular weight

Mol wt = 74.55 g / mole

0.1107 = 2.50 / 74.55 X volume in litres

volume = 0.303 Litres

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