[Joisu]

Hi everyone. My name is Joyce. I am in 11th grade. ^_^

Just started chemisty (hon) this year. It's been my second week. Haven't learned much yet. Anyway, the teacher gave us a few worksheets to work on. Need some help with it. I tried to answer a lot of them on my own (Please tell me if I am right and correct me if I am wrong!) but the ones written in red are the ones I don't know how to do at all. If you tell me the answers to those question, please tell me why they are the answers also.

Thank you very much. 11th grade is an important year for me. I hope to do well and get good grades! Please hele me! ^_^

1. Round off each of the following to the four significant figures: (a) 7.03846 g, (b) 15759 m, (c) 0.0028645 L, (d) 8.3100 x 10^6 J

My answers: (a) 7.0404 (b) 1.57 x 10^4 (c) 2.86 x 10^-3 (d) ?

2. Which of the following properties of a piece of gold foil intensive: thinkness, color, area, melting point, translucence, electrical resistance?

My answer: color (note: I don't know why. I am totally guessing...)

3. The density of gold g cm^-3. Which is heavier (has a larger mass): a 1-kg standard mass, or a cube of gold that measures 3.7 cm on each side.

4. The answer to the expression 8.735 g + 2.3 g + 93.683 g. to the correct number of significant figures is.... (a) 104.7 g, (b) 104.718 g, (c) 1.05 x 10^2 g, (d) 100g, (e) 104.6 g

My answer: (c)

5. Copper is a reddish-brown metal that is easily stretched to make wires. These characteristics are examples of (physical/chemical) properties of copper.

My answer: physical

6. Write each of the following as an "ordinary" decimal number:

a) 6.235 x 10^-2   b) 7.229 x 10^3   c) 5.001 x 10^-6   d) 8.621 x 10^4

My answers: a) .06235  b) 7229  c) .000005001  d) 86210

7. The thickness of a sheet of iron os 0.887. Its density os 7.86 g/cm^3. Its mass is 795 g. Calculate the area of the sheet iron.

8. Classift the following mixtures as homogenous or heterogeneous.

a) a jar of jellybeans b) gasoline c) chunky peanut butter d) margarine e) the paper on which this question is written.
Me: no idea what homogenouns and heterogeneous are....

9) For each of the following numbers, if the number is rewritten in standard scientific notation, what will be the value of the exponent (for the power of 10)?

a) 0.000067    b) 9,331,442   c) 1/10,000   d) 163.1 x 10^2

My answers: a) 6.7 x 10^-5  b) 9.3 x 10^7  c).. d)1.631 x 10^4

10. Indicate the number of significant figures in each of the following:

a) 1422   b) 65,321  c) 1.004 x 10^5  d) 200  e) 200.  f) 2.00 x 10^2   g) 435.662  h) 56.341

My answers: a) 4 (sig figs)  B) 5  c) 6  d) 3 (i don't get it....what's the difference between d and e...?) f) 3    g) 6    h) 5

11. Which weighs more, 4.25 grams of gold or 425 milligrams of gold?

My answer: 425 mil

12. Evaluate each of the following and write the answer to the appropiate number of sig fig

a) (4.031)(0.08206)(373.1)/(0.995)
b) (12.011)/(6.022 x 10^23)
c) (0.500)(44.02)
d) (0.15)/(280.62)

Okie, That is all for now. Thank you every much. ^_^

   

[Borek]

1. Round off each of the following to the four significant figures: (a) 7.03846 g, (b) 15759 m, (c) 0.0028645 L, (d) 8.3100 x 10^6 J

My answers: (a) 7.0404 (b) 1.57 x 10^4 (c) 2.86 x 10^-3 (d) ?

a - is it 7.0404 or 7.04? Probably a typo on your side.

Note that d is nothing else but 8,310,000 - what do we do with ending digits?

Hopefully someone will try to address other problems. Please read forum rules.

[Joisu]

Oh, sorry....In that case, I'll probably delete this post...

[constant thinker]

The main rule you violated was posting so many homework problems at once. Since you're new I'll cut you some slack and help by skimming through quickly.

Also check your spelling. There is a spell check button.

8. Classift the following mixtures as homogenous or heterogeneous.

a) a jar of jellybeans b) gasoline c) chunky peanut butter d) margarine e) the paper on which this question is written.
Me: no idea what homogenouns and heterogeneous are....

If you don't know what those 2 words are, google and wikipedia are your friends. Even a dictionary works. You could also use your text book.

http://dictionary.reference.com/search?q=homogeneous
http://dictionary.reference.com/browse/heterogeneous

5 is right.
6 looks right.
9 a and d are right. Check b. For c convert to decimal first.

For 11 you are comparing apples and oranges. Either convert both to grams or to milligrams.