(b) The density of platinum is 23.4 g/cm3 at 20°C. Calculate the mass of 77.0 cm3 of platinum at this temperature.
(c) The density of magnesium is 1.74 g/cm3 at 20°C. What is the volume of 275 g of this metal at this temperature?
*what I am stuck on the most is that the answer has to be in the correct of SIGNIFICANT FUGURES.<--I know what they are but I am not getting answer right at all! Please help, thanks:)
Good. Then you know how to work the density part of the problem. Here is a good web site that will explain significant figures. Feel free to post back here if you have questions from the link.
http://www.chemteam.info/SigFigs/SigFigs.html
Here is the first one to help you get started.
mass = volume x density
mass = 77.0 cc x 23.4 g/cc = 1801.80 grams.
In multiplication and division, you are allowed as many s.f. in the answer as you have in the smallest number of s.f. used in the calculation.
77.0 has 3 s.f.
23.4 has 3 s.f.
Therefore, you are allowed 3 s.f. in the answer. With an answer of 1801.80, the first 1,8, and 0 are significant. The second 1, second 8 and last 0 are not. So you write the answer as
1.80E3 grams.
Thanks a million "DrBob222" your example and website you provided me helped me out alot!!!:)
To calculate the mass of an object, you can use the formula:
Mass = Density × Volume
Let's start with question (b) first.
(b) The density of platinum is 23.4 g/cm3 at 20°C. To calculate the mass of 77.0 cm3 of platinum at this temperature, you can use the formula mentioned above.
Mass = Density × Volume
Mass = 23.4 g/cm3 × 77.0 cm3
When multiplying or dividing measurements with significant figures, you should consider the measurement with the fewest significant figures. In this case, the volume (77.0 cm3) has three significant figures, while the density (23.4 g/cm3) has three significant figures as well.
Therefore, the answer should also have three significant figures. Now let's perform the calculation:
Mass = 23.4 g/cm3 × 77.0 cm3
= 1801.8 g
Since we need to round to three significant figures, the final answer would be 1800 g.
Now let's move on to question (c).
(c) The density of magnesium is 1.74 g/cm3 at 20°C. To calculate the volume of 275 g of magnesium at this temperature, we'll rearrange the formula from question (b) to solve for volume:
Volume = Mass / Density
Volume = 275 g / 1.74 g/cm3
Again, we consider the measurement with the fewest significant figures, which in this case is the density (1.74 g/cm3) with three significant figures.
Therefore, the answer should also have three significant figures. Now let's perform the calculation:
Volume = 275 g / 1.74 g/cm3
= 158.333 cm3
Now, when rounding to three significant figures, we get 158 cm3 as the final answer.
Remember to always consider the significant figures in the given measurements, and use the least precise measurement to determine the number of significant figures in the answer.