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

• babyintel
In summary, the conversation is about a homework problem involving calculating the number of atoms in a sample of plumber's solder. The person asking for help is not confident in chemistry and needs to submit the problem online by tomorrow at 11pm. They are advised to calculate the mass of lead and tin in the sample first.

#### 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?

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.

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!

## 1. What is the problem you need help with?

The problem that I need help with involves a homework assignment that is due by 11pm on April 19, 2009.

## 2. What subject is the homework problem for?

The homework problem is for a science subject.

## 3. What specifically do you need help with?

I need help understanding and solving a specific question or task within the homework assignment.

## 4. What resources have you already tried?

I have tried referring to my notes, textbook, and online resources, but I am still struggling to find the answer.

## 5. Is there a specific format or method I should use to help you?

Yes, please provide clear and detailed explanations or step-by-step instructions on how to solve the problem. Visual aids or examples may also be helpful.