I got my midterm back and have a several question. Help me!!
1. Using the rules of significant figures, calculate the following 6.167 + 70
a) 76 b) 80 c) 76.167 d) 77 e) 76.17
In addition and subtraction, when you determine the significant figues, you look for the least decimal place, right? After calculate this problem, you would get 76.167 so if you were to change this to the least decimal place, wouldn't it be 76? I put A as an answer with a confidence and I got it WRONG!! The correct answer was b. Please explain. Thank you!!
2. Which of the following involves a chemical change?
a) boiling water b) melting ice c) chopping wood
d) cooking an egg e) none of these
I put E as an answer, but the correct answer is D.
I thought "cooking an egg" is a physical change, not a chemical change. Can anyone explain? Thank alot.
3. Which of these is a chemical property?
a) Ice melts at 0 degree Celcius.
b) Oxygen is a gas.
c) Helium is very nonreactive.
d) Sodium is a soft, shiny metal.
e) Water has a high specific heat.
Please explain. Thank you!
4. In a chemical change,
a) a phase change must occur
b) the original material can never be regenerated
c) a phase change never occurs
d) the products are different substances from the starting materials.
Please explain. I put A as an answer. Can anyone tell me why not A but D?? Thanks in advance.
5. A solution can be distinguished from a compound by its
a) variable composition b) liquid state
c) heterogeneous nature d) lack of color
I put C as an answer. Can anyone explain???
6. The law of constant composition applies to
a) metals b) metalloids c) homogeneous mixtures
d) heterogeneous mixtures e) compounds
I put C as an answer. Please explain. Thanks.
7. In chemistry, a formula is used to represent
a) a compound b) an element c) a metal
d) all of these e) none of these
I put D as an answer. Please explain. Thank you.
8. The average mass of a boron atom is 10.81. Assuming you were able to isolate only one boron atom, the chance that you would randomly get one with a mass of 10.81 is
a) 0% b) 0.81% c) about 11% d) 10.81% e) greater than 50%
I put C as an answer. Can anyone explain why A?? Thanks.
9. Choose the pair in which the components have the same charge.
a) a proton and a hydrogen atom
b) a hydrogen atom and an electron
c) a neutron and a hydrogen atom
d) an electron and a neutron
I put A as an answer. I thought it as having + charge for both proton and hydrogen, no? Please explain. Thanks.
THANK YOU SO MUCH. YOU DON'T HAVE TO ANSWER ALL OF THEM ALL AT ONCE. YOU MAY ANSWER THE ONES YOU KNOW.
HAVE A GOOD ONE!