The Borough of Mashattan Community The City University of New York Chemistry 201

Question

The Borough of Mashattan Community The City University of New York Chemistry 201 Final Examination Prut.vuma MULTIPLE CHO ICE Choose the one alternative that best completes the statement or answers the question 1) When the following equation is balanced, the coefficient of 1H25 is 1) A) 1 B) 4 C) 3 D) 5 E) 2 2) How many grams of oxygen are in 65 g of C2H202 2) A) 29 B) 130 C) 36 D) 18 E) 9.0 3) A 2.25- g sample of magnesium nitrate, Mg(NO3)2, contains mol of this compound. 3) A) 0.0261 B) 0.0152 C) 38.4 D) 65.8 E)148.3 4) What is the empirical formula of a compound that contains 27.0% S 13.4%, and 596% aby 4) mass? A) SOCI CISO4 E) SOCI2 5) A compound that is composed of carbon, hydrogen, and oxygen contains 70.6% C, 5.9% H, and 23.5% O by mass. The molecular weight of the compound is 136 amu. What is the molecular 5) formula? A) C4H4C E) C9H120 6) The combustion of ammonia in the presence of excess oxygen yields NO2 and H20. 6) NH3 (g) 702 (g) -4 NO2 (8) 6H20(8) The combustion of 43.9 g of ammonia produces g of NO2- A) 119 B) 43.9 C)2.58 D) 0.954 E) 178 7) 7) The combustion of propane (C3H8) produces CO2 and H20: C3Hs (g)+502 (8)-3CO2 (8) 4H20 (8) The reaction of 2.5 mol of 02 will producemol of H2O. A) 4.0 B) 3.0 C) 2.5 D) 2.0 E) 1.0 8) There are hydrogen atoms in 25 molecules of C4H4S2 A)38.1024 B)15. 1035 25 D) 6.0 1025E) 100 Version A

Explanation / Answer

8.

In 1 molecule of C4H4S2, there are 4 hydrogen atoms

So, in 25 molecule of C4H4S2, there are (25 x 4 = 100) hydrogen atoms

Answer is option (E) 100

7.

C3H8(g)   +   5O2(g)   ----->   3CO2(g)   +   4H2O(g)

In the above reaction equation is balanced. In the balanced reaction equation
5 moles of O2 produces 4 Moles of H2O
1 moles of O2 produces (4/5) Moles of H2O
2.5 moles of O2 produces 2.5 x (4/5) Moles of H2O
2.5 moles of O2 produces 2 Moles of H2O

Answer is option (D) 2.0

6.

4 NH3(g)   +   7O2(g)   ----->   4NO2(g)   +   6H2O(g)

In the above balanced reaction equation

4 moles of NH3 produces 4 moles of NO2
or, 1 moles of NH3 produces 1 moles of NO2

43.9 g of NH3
Molar mass of NH3 = 17 g/mol
So, 17 g of NH3 = 1 mol
1 g of NH3 = (1/17) mol
43.9 g of NH3 = (43.9/17) mol = 2.58 mol

So, NO2 produced = 2.58 mol
Molar mass of NO2 = 46 g/mol
So, 1 mole of NO2 = 46 g
2.58 mole of NO2 = 2.58 x 46 g = 118.68 g = 119 g

Answer is option (A) 119

1.

FeCl3(aq)   +   H2S(g)   ------->     Fe2S3(s)   +   HCl(aq)

Balancing the Fe and S
2FeCl3(aq)   +   3H2S(g)   ------->     Fe2S3(s)   +   HCl(aq)

Balancing H and Cl, we get
2FeCl3(aq)   +   3H2S(g)   ------->     Fe2S3(s)   +   6HCl(aq)

So, the coefficient of H2S is 3

Answer is option (C) 3

2.

65 g of C2H2O2
Molar mass of C2H2O2 = 58 g/mol
So, 58 g of C2H2O2 = 1 mol
or, 1 g of C2H2O2 = 1/58 mol
or, 65 g of C2H2O2 = 65/58 mol = 1.12 mol

Now,

In 1 mole of C2H2O2, moles of oxygen = 2 mol
or 1.12 mole of C2H2O2, moles of oxygen = 1.12 x 2 mol = 2.24 mol

Molar mass of oxygen = 16 g/mol
So, 1 mole of oxygen = 16 g
or, 2.24 mole of oxygen = 2.24 x 16 g = 35.84 g = 36 g

Answer is option (c) 36.

3.

Molar mass of Mg(NO3)2 = 148.3 g/mol
So, 148.3 g of Mg(NO3)2 = 1 mol
or, 1 g of Mg(NO3)2 = (1/148.3) mol
or, 2.25 g of Mg(NO3)2 = (2.25/148.3) mol = 0.0152 mole

Answer is option (B) 0.0152

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