[XxXCausticxXx]

   These are the small handful of problems I'm having trouble solving, any help + general advice would be greatly appreciated.

1.) If density of gold is 19.3 g/cc, then calculate the mass of the gold bar if it occupies 10 cc (It is useful to know that 1cc = 1mL)      

   Answer on my teacher's document said 200, and I get 193, pretty sure I'm correct.

2.) How many kilograms of sodium fluoride (NaF) are required, per year, to obtain a concentration of 1 ppm fluoride in the water supply of a town with 150,000 people, where each each person consumes 660 L of water per day?  Sodium fluoride is 45.0% fluoride by mass; water has a density of 1.00 g/cm3

   I kind of got close to answering this one, I just had no way of figuring 1 ppm, I don't know what it is, she never told us in class, and I researched it online and just got confused even more.

3.) What percent of the first 36 elements on the periodic table are solids at room temperature.
A 225-g sample of aluminum was heated to 125.5 *C, then placed into 500.0 g water at 22.5*C to its melting temperature, 327.5C*. What is the specific heat of this metal?

   I was a good 4% off, it seems to vary with what periodic table I use, is there a standard one that is mostly fallowed? Dynamic Periodic table I remember calculating to around 75-80%

A carbon atom has a radius of 77 picometers. Calculate the volume of a carbon atom in cubic   meters (V = 4/3 pi r3).  ( 1 pm = 10-12 m)

4/3rd's pi? how do I calculate this. 

525 mL of water at 25°C (density = 0.997 g/mL) is placed in a container. The water is then cooled to form ice at –10°C (density = 0.917 g/mL). What is the mass and volume of the ice?

   How do I find the mass of Volume of the ice?

   Do you think it's a good idea to read and take notes, just do lots of problems? I'm 4 weeks into this class and everything kinda feels "the other way round" and I've already failed my first exam because of questions like the ones I just posted, also, my teacher throws out these really general questions and treats them like they're emperical; this was one of the exam questions, "choose the homogenous mixture from the list below"

Also, what are your opinions on using calculators for math classes and science classes such as chemistry? do you think it is a requirement? can you survive without one? As you progress through chemistry (I know it is cumulative) does your knowledge of math also need rise???

a.) kool-aid
b.) mud
c.) ice water
d.) salad dressing
e.) salsa.

   For what reasons/facts are any of the above homogenous? aren't they all heterogenous mixtures? /:

   Sorry for seeming a bit on the slow slide, this is my first chemistry class and I'm only 4 weeks into it. (this work is already a week old, I keep all the problems that confuse me/baffle me so I can figure out how to solve them as I progress through the course.

|8<

[Dan]

1. I agree with you

2. ppm = parts per million. http://en.wikipedia.org/wiki/Parts-per_notation#Overview. It just means "x per million x" where x is some unit of measurement, in this case mass - so "grams per million grams" for example.

3. Show your working for the percentages otherwise we can't tell what you're doing wrong. Also, you have not attempted the specific heat question.

4. π is a constant, there is a button on your calculator for it (or at least there should be). If you don't have a calculator, π ≈ ²²/₇ is a pretty good approximation.

5. Water and ice question: What is the mass of water? So what is the mass of ice?

6. Doing practice problems is extremely important. Getting a basic foundation in a topic by note-taking is essential, but the real understanding of a topic comes only with practice.

7. If you do not have a calculator, you are making life unnecessarily difficult for yourself. The maths in chemistry does get harder, but it is generally just algebra until you get to university (I think, depends on school/country etc.).

8. What are the definitions of heterogeneous and homogeneous?

[Arkcon]

   These are the small handful of problems I'm having trouble solving, any help + general advice would be greatly appreciated.

1.) If density of gold is 19.3 g/cc, then calculate the mass of the gold bar if it occupies 10 cc (It is useful to know that 1cc = 1mL)      

   Answer on my teacher's document said 200, and I get 193, pretty sure I'm correct.

Significant figures?

[Sophia7X]

   Do you think it's a good idea to read and take notes, just do lots of problems? I'm 4 weeks into this class and everything kinda feels "the other way round" and I've already failed my first exam because of questions like the ones I just posted, also, my teacher throws out these really general questions and treats them like they're emperical; this was one of the exam questions, "choose the homogenous mixture from the list below"

Also, what are your opinions on using calculators for math classes and science classes such as chemistry? do you think it is a requirement? can you survive without one? As you progress through chemistry (I know it is cumulative) does your knowledge of math also need rise???

|8<

Yeah, looks like #1 is a sig figs thing. 10 has 1 significant figure so the answer also has 1 significant figure.

And yes, it is definitely a good idea to read, take notes, and do problems. 75% of your studying time should involve working out problems. Chemistry is a lot like math, you learn mostly by doing problems and seeing what kind of mistakes you make.

In my chem class, we couldn't use calculators on tests but we could use them on quizzes. In my opinion, restricting the use of calculators in chemistry is pretty pointless since it isn't about how well you can do mental math. Higher level chemistry does require higher level math (i.e. calculus instead of just algebra).