Please I need help in Chem!

Question

I need help on my last 3 problems of my Chemistry homework please!

1) A block of lead, with dimensions 2.0 dm X 8.0 cm X 35 mm, has a mass of 6.356 kg. Calculate the density of lead in g.cm^3

2) Demonstrate that kg/L and g/cm^3 are equivalent units of density.

3) In the manufacture of steel, pure oxygen is blown through molten iron to remove some of the carbon impurity. If the combustion of carbon is efficient, carbon dioxide (density = 1.80g/L) is produced. Incomplete combustion produces the posionous gas carbon monoxide (density=1.15g/L) and should be avoided. If you measure a gas density of 1.77g/L, what do you conclude?

Those are my 3 questions that I do not understand. I would gladly appreciate the time and effort that you have done to help me out. Thanks!

Answer 1

1.  Asks for your answer in g x cm^3

  which is wrong.  It is g / cm^3

grams per cubic centimeter

gives data in kilograms and a variety of length units

need to convert to g and cm

if you have the mass and the volume of a material you just divide the one by the other to get density.

You have been taught what the various units mean so you SHOULD know how to convert.

2.  You were sleeping during class?  Shame.  Science and Math are cumulative subjects.  That means that while you can blow off European History one week and still get a good grade in US History, in science and Math the knowldege is built on what you SHOULD have previously learned.  If you didn't learn it you are in for a rough time.

To demonstrate, convert 1 kg per Liter into g per cm^3

3.Pure CO2 is 1.8 g/L; pure CO is 1.15 g/L  what you have is 1.77 g/L

Surely it is obvious to you that it is a mixture of CO2 and CO?!?!  (Or some totally unrelated material like hydrogen and water)

you have to be careful when dealing with density:

One liter would weigh 1.77 g, to figure out how much of each gas you have you set up an equation for one liter (it could be any volume, but one liter is easiest)

SO what do you know?   1 L of mix = A + B where A & B are the volumes of the two gasses CO2 and CO

Also since we know that the density of A is 1.8, if A is in liters then

1.8xA= mass of A in mix

same with B, 1.15xB= mass of B in mix

but since we know the density of the mixture we know waht the total mass is:1.77

So

1.8A+1.15B = 1.77

B = 1 - A

so

1.8A+ 1.15(1-A) = 1.77

1.8A+1.15 - 1.15A = 1.77

0.65A + 1.15 = 1.77

0.65A  = .62

A = 0.62/.65

etc.

Answer 2

1)  2.0 dm = 20cm

8.0 cm = 8.0 cm

35 mm = 3.5 cm

6.356 kg *(1000g/1kg) =6356 g of lead

Density= mass/volume

volume = 20*8.0*3.5=560 cubic cm

6356g/560cm^3=11.35 g/cm cubed (Density of lead)

2) 1 Kg/L = 1 g/mL = 1 g/cm^3

3) I'm not sure if u have to calculate anything on this one...I would just say Carbon Dioxide has been produced.