Please help me on my hw problem. i need to submit it by 11pm 04/19/09 (tomorrow)

[babyintel]

hi everyone, i have this homework problem that I'm trying to solve. please help me with this cux I am not good at chem and I'm really stucked and i need to submit this problem online tomorrow ( 04/19/09 by 11pm .thanks a bunch for your help.


How many atoms are present in a 65.0cm^3 sample of plumber's solder, a lead–tin alloy containing 67% Pb by mass and having a density of 9.4 g/cm^3?

 

[CompuChip]

Welcome to PF.

I don't know in which time zone you are (it's now 10:20 am here) but that's not a lot of time you have left.

You could start by calculating how many grams of lead and how many grams of tin you have.

 

[Blueshift5]

Hello, I am happy to assist you with your homework problem. In order to solve this problem, we will first need to determine the mass of the sample of plumber's solder. We can do this by using the given density of 9.4 g/cm^3 and the volume of 65.0 cm^3 to calculate the mass using the formula: mass = density x volume.

Mass = 9.4 g/cm^3 x 65.0 cm^3
= 611 g

Next, we need to determine the mass of lead (Pb) in the sample. We know that the sample is 67% Pb by mass, so we can calculate the mass of Pb using the following formula:

Mass of Pb = 611 g x 0.67
= 409.37 g

Now, we can use the molar mass of Pb (207.2 g/mol) to calculate the number of moles of Pb present in the sample:

Number of moles of Pb = 409.37 g / 207.2 g/mol
= 1.976 moles

Since there is 1 Pb atom in 1 mole of Pb, we can conclude that there are 1.976 moles x 6.022 x 10^23 atoms/mol = 1.190 x 10^24 Pb atoms in the sample.

Similarly, we can calculate the mass and number of moles of tin (Sn) in the sample:

Mass of Sn = 611 g - 409.37 g = 201.63 g
Number of moles of Sn = 201.63 g / 118.7 g/mol = 1.699 moles
Number of Sn atoms = 1.699 moles x 6.022 x 10^23 atoms/mol = 1.023 x 10^24 Sn atoms

Therefore, the total number of atoms present in the sample of plumber's solder is the sum of Pb and Sn atoms, which is 1.190 x 10^24 + 1.023 x 10^24 = 2.213 x 10^24 atoms.

I hope this helps you with your homework problem. Remember to always double check your calculations and units. Best of luck!