Practice exam 1

CHEM 1311 PRACTICE EXAM I (Chapters 1- 3)

Multiple Choice: Select one best answer.

1. Convert 0.3980 m to mm.

A)

B)

C)

D)

E)

2. A scientist obtains the number 0.0470056800 on a calculator. If this number actually has three (3) significant figures, how should it be written?

A)

0.0470

B)

0.047

C)

0.4700

D)

0.047006

E)

0.47006

3. Perform the indicated operations and express the answer with the proper number of significant digits. 28.1 cm + 0.53 cm + 75.321 cm =
A) 104
B) 1.04 x 102
C) 103.95
D) 103.951

E) 104.0

4. How many significant figures are appropriate to show in the result after carrying out the operation below?
(223.7 + 0.27) ÷ 4.21 =?
A) 1 B) 2 C) 3 D) 4 E) 5

5. What is the equivalent temperature for 98.6 Fahrenheit in Kelvin?
(a) 37 (b) 310 (c) 471.6 (d) 594.8 (e) -273.1

6. An unknown sample has a mass of 13.9 g and a volume of 17.4 mL. What is its density (g/mL)?

(a) 0.799 (b) 1.04 (c) 3.16 (d) 4.62 (e) 5.07

7. Which of the following is a heterogeneous mixture?
(a) milk (b) salt, water, and sugar (c) oil and water (d) 14-K gold ring (e) air
8. Which of the following is a physical change?
A) Color of carpet faded (by sun light)
B) Zinc strip dissolves in vinegar (to produce hydrogen gas)
C) Burn a wood block
D) Water freezes

E) Iron rusts

9. How many protons, electrons, and neutrons are there in 72Br- ?
(a) 35p, 35e, 72n (b) 34p, 35e, 37n (c) 35p, 36e, 72n
(d) 36p, 34e, 72n (e) 35p, 36e, 37n

10. Which of the following pairs would have similar chemical and physical properties?
(a) Ni, Mg (b) H, Na (c) C, Si (d) Cu, Ca (e) Cr, Cl
Hint: The elements from the same group (i.e. the vertical column) will have similar physical and chemical properties.

11. Which of the following is a molecular compound?
(a) KCl (b) CsF (c) HCN (d) AlBr3 (e) NaOH
Hint: Molecular compound is composed by nonmetal reacts with nonmetal atoms.

12. Which of the following is not a correct match?
(a) AlCl3, aluminum chloride (b) H2O dihydrogen monoxide
(c) CrF3, chromium (III) fluoride (d) HNO3, nitrous acid

(e) CuSO4.5H2O, copper (II) sulfate pentahydrate

13. Which of the following pairs is a correct match?
(a) Ba3(PO4)2, barium (II) phosphate
(b) (NH4)2SO4, diammonium sulfate (c) Na2O2, sodium oxide

(d) Ca(NO3)2, calcium nitrate (e) CH3COOH, carbonic acid

14. The atomic masses of 10B and 11B are 10.0129 amu (natural abundance 19.78%) and 11.0093 amu (natural abundance 80.22%), respectively. What is the average atomic mass of B?
(a) 9.467 (b) 9.966 (c) 10.042 (c) 10.504 (e) 10.810

Hint: You must convert the % into decimals first and then apply the formula and memorize it: M = M1X1 + M2X2 = 10.0129×0.1978 + 11.0093×0.8022 = 10.810.

15. What is the molar mass for calcium nitrate, Ca(NO3)2?
(a) 44 (b) 56 (c) 87 (d) 93 (e) 164

16. How many hydrogen atoms are there in 48.0 g of CH4?
(a) 1.81×1023 (b) 7.22×1024 (c) 6.02×1023 (d) 1.20×1025 (e) 4.70×1025

17. What is the mass percent (%) for O in SO2?
(a) 38.09 (b) 45.41 (c) 50.00 (d) 53.86 (e) 56.43

18. Which of the following is the empirical formula?
(a) C8H18 (b) CH3COOH (c) C4H10O2 (d) NH4NO3 (e) B2H6
Hint: Empirical formula is the simplest integral ratio among each atom.

19. Chemical analysis shows the composition of a compound containing carbon, hydrogen, chlorine, and oxygen, to be 37.84% C, 2.12% H, 55.84% Cl, and 4.20% O. What is its empirical formula?
(a) CHClO (b) C2HClO4 (c) C12H8Cl6O (d) C12H8Cl6O4

20. Chemical analysis shows the composition of a compound containing carbon and hydrogen, to be 80.00% carbon and 20% hydrogen and the molar mass is 30 g. What is its molecular formula?
(a) CH (b) C2H4 (c) C2H6 (d) C6H12 (e) C10H22

21. What are the coefficients respectively when the equation

__PH3 + __O2 __P2O5 + __H2O is balanced?

(a) 2, 2, 1, 3 (b) 2, 1, 3, 4 (c) 2, 3, 1, 2 (d) 2, 4, 1, 3 (e) 1, 1, 3, 3

22. In the reaction of Al(OH)3 with H2SO4, how many moles of water can be produced If the reaction is begun with 5.500 mole of Al(OH)3?
2Al(OH)3 + 3H2SO4 Al2(SO4)3 + 6H2O
(a) 2.50 (b) 4.75 (c) 6.32 (d) 7.58 (e) 16.50

23. How many grams of H2O could be formed by the reaction of 16.0 g of CH4 with 48.0 g of O2?

CH4 + 2O2 CO2 + 2H2O

(a) 27.0 (b) 37.3 (c) 46.8 (d) 54.1

24. What is the excess reagent in the above reaction (Q.23)of CH4 and O2? How many grams of the excess reagent were consumed?

(a) CH4, 12 grams (b) O2, 12 grams (c) CH4, 4 grams
(d) O2, 4 grams (e) CH4, 8 grams

25. A 15.6 grams of benzene (C6H6) is mixed with excess HNO3 to prepare nitrobenzene (C6H5NO2). After the reaction there are 15.6 grams of nitrobenzene produced. What is the percent yield of nitrobenzene?

C6H6 + HNO3 C6H5NO2 + H2O

(a) 34.3% (b) 47.6% (c) 58.9% (d) 63.4% (e) 71.2%

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