Help with Chemistry homework please. Thank you!
1. List and describe two differences between pure substances and mixtures. (Check all that apply).
a. Mixtures can be separated into their components only by chemical changes; some pure substances can be separated into components by physical change.
b. Mixtures can be separated into their components by physical changes; some pure substances can be separated into components by chemical change.
c. The composition of a pure substance depends on the source, but the composition of a mixture doesn't depend on the source.
d. The state of a pure substance is always the same, but the state of a mixture can vary.
e. The composition of a pure substance is always the same, regardless of the source, but the composition of a mixture can vary.
2. Which of the following is a physical change?
a. the condensation of water vapor
b. the rusting of iron
c. the baking of a potato
d. the explosion of nitroglycerin
3. Identify the product(s) in the following reaction: calcium carbonate → calcium oxide + carbon dioxide
a. calcium carbonate + calcium oxide + carbon dioxide
b. carbon dioxide + calcium carbonate
c. calcium carbonate
d. calcium oxide + carbon dioxide
e. calcium carbonate + calcium oxide
4. Which best describes the size and shape of a sample of gas?
a. Volume and shape are both determined by the container.
b. It has definite volume and definite shape.
c. It has definite volume, but shape is determined by the container.
d. Volume and shape cannot be described.
e. Its volume is determined by the container, but it has a definite shape.
5. A 440g sample of mercury and a 160g sample of iron are at an initial temperature of 25.0 degree Celsius. 250 cal of heat is applied to each sample.
Substance : Specific Heat [ cal/ (g x degree Celsius)]:
a. What is the final temperature of mercury sample? (Express your answer using two significant figures).
b. What is the final temperature of iron sample? (Express your answer using three significant figures).
6. The conversion factor used to convert 55.6 km to miles is?
a. 1km / 1.61miles
b. 1mile / 1.61km
c. 1km / 1000m
d. 1.61miles / 1km
e. 1.61km / 1mile
7. Which of the following observations demonstrates that a solid sample is a compound?
a. It cannot be broken down into simpler substances by chemical methods.
b. Heating the substance causes no visible color change.
c. Crushing the sample does not affect its other properties.
d. It cannot be broken down into simpler substances by physical methods.
e. Heating the substance causes it to melt, then to boil.
8. How many electrons are present in an atom with its 1s, 2s, 2p subshells filled? (Express your answer as an integer).
a. N = ______ ?
b. What is this element? Express your answer as a chemical symbol.
9. Identify the group 5B element in period four. (Express your answer as a chemical symbol).
10. Which elements all belong in the same group?
a. F, Cl, Br
b. Fe, Cu, Ni
c. C, N, O
d. Al, Ge, Sb
e. B, Si, As
11. Nitrogen, has two naturally occurring isotopes: N-14 (99.64%; 14.00 amu) and N-15 (0.36%; 15.00 amu). Write the symbols for both. (Express your answers as isotopes
separated by a comma).
12. How many electrons can occupy the 4d subshell?
a.1 b. 8 c. 6 d. 2 e. 10
13. Locate and identify the group number for each of the following transition metals:
14. How many electrons are present in an uncharged atom with its 1s, 2s, 2p, 3s, 3p, and 4s subshells filled and with two electrons in the 3d subshell? (Express your answer as
an integer). What is the element symbol for this element? (Express your answer as a chemical symbol).
15. The number of valence electrons in a main group element is given by ________.
a. the element's group number
b. the element's atomic number
c. the element's atomic weight
d. none of the above