[cœur_vaillant]

These are a couple of questions i must submit to a prof.  If someone could look over them and make sure that the steps/answers (in significant figures) are correct that would be much appreciated.  If there are mistakes an explanation as to why and a possible correction would be very helpful. Many thanks in advance. 

I.

Q: a cube of osmium metal 1.500 cm on a side has a mass of 76.31 g at 25 degrees celcius. What is the density in g/cm³ at this temperature?

A:

(1) volume of cube : (1.500)³ = 3.375cm³

(2) Density = mass/volume
= 76.31 g/3.375 cm³
= 22.61g/cm³

Therefore, the density of osmium metal at 25 C is 22.61 g/cm³
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II.

Calculate the number of grams of sulphuric acid in 0.500L of battery acid if the solution has a density of 1.28g/mL and is 38.1% sulphuric acid by mass.

A:

(1) Convert L to mL = 500 mL of battery acid
(2) D = m/V => m = D x V
(3) m = D x V
= 1.28 g/mL x 500 mL
= 640 g
(4) mass of Solution is 38.1% sulphuric acid ; therefore 38.1% of 640g =(approx.) 243.85 g

Therefore, the number of grams of sulphuric acid is 243.85

[AWK]

Density OK. Round mass to 3 significant digits