Indicate the anwer choice that best completes the statement or answers the guest

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Indicate the anwer choice that best completes the statement or answers the guestion 1. Pure copper may be produced by the reaction of copper(T) sulfide with oxygen gas as follows ir the reaction of o.200 kg of copper) sulfide with excess oxygen produces 0.190 kg of copper metal, wh percent yield a, 679 % b.399 % c. 271 % d, 135 % e, 33.9 % 2. The reaction of 11.9 g of CHCl, with excess chlorine produced 10.0 gof CCl, carbon tetrachloride What is the percent yieldi a, 84.0% b, 100% c, 652 % d, 326 % e, 43.5 % 3. A misture of MnSO, and MnSO, 4HO has a mass of 2.005 g. After heating to drive off all the water the 1.780 g. What is the mass percent of MnSO4 4H-0 in the mixture? a, 11.2% b, 34.7% c. 65.3% d, 69.6% e, 888% 4. Of the following, the only empirical formula is 5. A compound consists of only C and F. It contains 17.39% C by mass. what is the empirical formula ofthe 6. What is the pH of 2.9 103 M H? a.-1.01 b. 254 c. 3.50 d. 1.01 e 565 7.Aspirin is produced by the reaction of salicylic acid (Mf- 138.1 g/mol) and acetic anhydride (MM 102.1 gh Ir2.04 g of CoHgO& (M- 180.2 gimol) is produced from the reaction of 3.03 gCH,0 and 4.01 gCH the percent yield? a.288% b, 29.0% c.509% d, 51.6% e, 673% 8. The pH of a vingar solution is 4.15. What is the HO·concentration ofthe solution? a. 7.1 x 10- M b, 1.6 x 10-2 M c. 0.62 M d. 1.4M e, 1.4× 104 M 9. How many moles of sodium bromide can be produced from the reaction of 1.03 moles of sodium with 0.6 bromine gas? 2Na(s) + Br2(g) 2 NaBr(s) a. 0.650 mol b. 1.03 mol .1.30 mol d. 2.06 mol e.0515 mol

Explanation / Answer

10) nitric acid is a strong acid so we will assume complete dissociaiton of nitric acid

pH= 2.15 = -log[H+]

[H+]= 0.0071 moles / L = [HNO3]

Molecular weight of HNO3 = 63g / mole

Mass in 1L = molarity X molecular weight = 0.0071 X 63 = 0.4473 g / L

So mass in 20L = 0.4473 X 20 = 8.946grams

11) as per stoichiometry of reaction 6 moles of Mg will react with 1mole of P4 to give 2 moles of Mg3P2

Here the limiting reagent is P4

0.020moles of P4 will react with = 0.02 X 6 moles of Mg = 0.12moles of Mg

these moles of P4 and Mg will react to give 2 X 0.02 moles of Mg3P2 = 0.04 moles of Mg3P2

12) As per the equation 2 moles of Hcl will react with one mole of Na2CO3

Moles of HCl used =Molarity X volume (L) = 0.1082 X 15.66 /1000 = 0.00169 moles

Moles of Na2CO3 reacted = 0.5 X 0.00169 = 0.000847 moles

Molecualr weight of Na2CO3 = 106g / mole

Mass of Na2CO3 reacted = Moles X molecular weight = 0.000847 X 106 = 0.0898 grams

the mass of soda ash taken = 0.1800 grams

% of Na2CO3 = 0.0898 X 100 / 0.1800 = 49.89% (purity)

13) Mass of titanium = 1.89grams

Moles of titanium = MAss / atomic weight = 1.89 g / 47.9 g / mole = 0.0395 moles

Mass of chlorine = 6.10 grams

Moles of Chlorine = Mass / atomic weight = 6.10 / 35.5 = 0.172 moles

Let us divide moles of chlorine with moles of Ti

0.172 / 0.0395 = 4.3 = 4 (approx)

So the empriical formula will be TiCl4

14) the mass of Calcium in one mole of calcium oxalate= 40grams

Molecular weight of calcium oxalate = 128g / mole

40g of Ca in 128g of calcium oxalate

the weight of calcium oxalate = 11grams

So mass of calcium in it = 40 X 11 / 128 = 3.44 grams

% of calcium in sample = 3.44 X 100 / 15 = 22.93%

15)

moles of Br2= Mass / Molecular weight = 5 / 159.8 = 0.0313 moles

Moles of NH3 = Mass / Molecular weight =1.10 / 17 = 0.065 moles

here three moles of Br2 will react with 8 moles of NH3

Here limiting reagent is Br2

0.065 moles of NH3 will react with 0.0244moles of Br2

three moles of Br2 will react with NH3 to give six moles of ammonium bromide

0.0244moles of Br2 will react with NH3 to give = 6X0.0244 / 3 = 0.0488 moles

Mass of ammonium bromide formed = Moles X molecular weight = 0.0488 X 97.94 g / mole = 4.78grams

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