chem 140

1234 words 5 pages
Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.
__A__ 1. The weight of an object is a. a measure of the gravitational force pulling the object toward the earth. b. equal to the mass of the matter in the object. c. a measure of the space occupied by the object. d. the same at any location on the earth. ___B_ 2. The melting of ice to liquid water is correctly classified as a. a chemical change c. both a chemical and a physical change b. a physical change d. neither a chemical nor a physical change _B___3. As two clear liquid solutions are added together, a red solid forms. This change is most likely a. physical c. neither chemical nor
…show more content…
Atoms are neutral. How can they have no charge? a. equal numbers of protons and neutrons b. equal numbers of protons and electrons c. equal numbers of neutrons and electrons d. any charge has been drained out of the atom
__C__ 24. What is the reason that U-238 is different from U-235? a. three more electrons c. three more neutrons b. three more protons d. there is no difference __B__ 25. How many neutrons are found in the nucleus of a boron-11 (b) atom? a. 11 b. 6 c. 5 d. 4 _A___ 26. Avogadro's number of iron (Fe) atoms would weigh a. 55.9 g b. 27.9 g c. 6.02 × 1023 g d. 6.02 × 10-23 g
_B___ 27. How many atoms are contained in a sample of krypton, Kr, that weighs 8.38 g? a. Avogadro's number c. one b. one-tenth Avogadro's number d. one-tenth _D___ 28. Which of the following has the largest mass? a. 5.0 mol H2O b. 3.5 mol NH3 c. 8.0 mol C d. 6.0 mol C2H2 __A__ 29. How many silicon atoms (Si) are contained in a 12.5 g sample of silicon? a. 2.68 × 1023 b. 5.83 × 10-22 c. 1.35 × 1024 d. 1.71 × 1021
_B__ 30. How many moles of oxygen atoms are in one mole of CO2? a. 1 b. 2 c. 6.02 × 1023 d. 12.04 × 1023
__A__ 31. What is the weight percentage of nitrogen in urea, CN2H4O? a. 46.7 b. 30.4 c. 32.6 d. 16.3

___D_ 32. How many carbon atoms are contained in 5.50 g of ethane, C2H6? a. 2.75 × 10-22 b. 3.29 × 1024 c. 1.10 × 1023 d. 2.21 × 1023

B____ 33. How many grams of iron (Fe) is contained in 15.8 g of Fe(OH)3? a. 12.1