can some one help me with a few chem questions please.

A chunk of iron weighs 4.32 g.
a) How many iron atoms are there in this sample?

55.85 g Fe = 1.00 mol Fe = 6.022 x 1023 atoms Fe

b) How many moles of iron are there in this sample?

2. . You have a copper bar weighing 71.24 g and a silver disk weighing 98.50 g. Which sample has the greater number of atoms, and how many more atoms are there in the one than the other?

3. a)How many moles of compound are present in 221 g of ammonium chloride, NH4Cl?
b)How many moles of hydrogen are in this sample?

A chunk of iron weighs 4.32 g.

a) How many iron atoms are there in this sample?

55.85 g Fe = 1.00 mol Fe = 6.022 x 1023 atoms Fe
mols Fe = grams Fe/55.85
Then mols Fe x 6.022E23 = ? no. atoms.


b) How many moles of iron are there in this sample?

See above.

2. . You have a copper bar weighing 71.24 g and a silver disk weighing 98.50 g. Which sample has the greater number of atoms, and how many more atoms are there in the one than the other?
mols Cu = grams Cu/atomic mass Cu=?
Then mols Cu x 6.022E23 = number Cu atoms. Compare with other answer and subtract.


3. a)How many moles of compound are present in 221 g of ammonium chloride, NH4Cl?
mols = grams NH4Cl/molar mass NH4Cl = ?

b)How many moles of hydrogen are in this sample?
There are 4 mols H in each mol NH4Cl; therefore, there are 4x mols NH4Cl of H

1. i do not understand your explaination.

2. i do not understand explaination.

3. a i don't understand, so b is 16?

OK, so I'll start over. Below I have erased all I wrote but kept what you wrote. My response is in bold.

A chunk of iron weighs 4.32 g.
a) How many iron atoms are there in this sample?

55.85 g Fe = 1.00 mol Fe = 6.022 x 1023 atoms Fe
What you have written is exactly right. 55.85 is the atomic mass Fe, 55.85 grams is 1 mol Fe and there are 6.022E23 atoms in 1 mol. So how many mols Fe are there in 4.32 g Fe? I wrote that mols Fe = grams atomic mass so 4.32/55.85 = approx 0.078 mols (but you need to do it more accurately). If there are 6.022E23 atoms in 1 mol then there must be approx 0.078 x 6.022E23 = ? atoms in 0.078 mols. Again, you need to do it more accurately.

b) How many moles of iron are there in this sample?
I calculate the mols Fe in that 4.32 sample above.

2. . You have a copper bar weighing 71.24 g and a silver disk weighing 98.50 g. Which sample has the greater number of atoms, and how many more atoms are there in the one than the other?
You calculate the mol Cu (same process as above) in the 71.23 g Cu and calculate atoms Cu in that many mols (again, same process as above), then compare atoms Cu in 2 with atoms Fe in 1 to see which is larger, then subtract the larger number from the smaller number to find the difference.

3. a)How many moles of compound are present in 221 g of ammonium chloride, NH4Cl?
From above, mols = grams/molar mass; therefore, in 221 g NH4Cl you will have 221/approx 53.5 = approx 4 mols NH4Cl.

b)How many moles of hydrogen are in this sample?
There are approx 4 mols NH4Cl. You have 4 mols H atoms for every mol of NH4Cl; therefore, there must be approx 4 x 4 = approx 16. The number isn't exactly 16; I obtained 4.13 mols NH4Cl so you will have 4 x 4.13 = 16.5 mols H atoms.
Anna Friday, November 13, 2015 at 1:28pm

1. i do not understand your explaination.

2. i do not understand explaination.

3. a i don't understand, so b is 16?

number 1a is 4.66x10^23, atoms Fe

number 1b is .0774mol Fe

number 2 is 1.25x10^23 more atoms of
copper

number 3a is 4.13 mol ammonium chloride

number 3b is 16.52 mol H

To answer these questions, we will use the concept of molar mass and Avogadro's number.

1) a) To find the number of iron atoms in the given sample, we need to convert the mass of the iron to moles and then use Avogadro's number.

Given: Mass of iron = 4.32 g, Molar mass of iron (Fe) = 55.85 g/mol, Avogadro's number = 6.022 x 10^23 atoms/mol.

First, we need to calculate the number of moles of iron:
Moles of iron = Mass of iron / Molar mass of iron
Moles of iron = 4.32 g / 55.85 g/mol = 0.07734 mol

Next, we can calculate the number of iron atoms:
Number of iron atoms = Moles of iron * Avogadro's number
Number of iron atoms = 0.07734 mol * 6.022 x 10^23 atoms/mol = 4.65 x 10^22 atoms

Therefore, there are approximately 4.65 x 10^22 iron atoms in the given sample.

b) To find the number of moles of iron in the sample, we already have this value from part a:
Number of moles of iron = 0.07734 mol

2) To compare the number of atoms in the copper bar and the silver disk, we will again use the concept of moles and Avogadro's number.

Given: Mass of copper bar = 71.24 g, Mass of silver disk = 98.50 g, Molar mass of copper (Cu) = 63.55 g/mol, Molar mass of silver (Ag) = 107.87 g/mol, Avogadro's number = 6.022 x 10^23 atoms/mol.

First, we can calculate the number of moles for each sample:
Moles of copper = Mass of copper / Molar mass of copper
Moles of copper = 71.24 g / 63.55 g/mol = 1.12 mol

Moles of silver = Mass of silver / Molar mass of silver
Moles of silver = 98.50 g / 107.87 g/mol = 0.912 mol

Next, we can calculate the number of atoms for each sample:
Number of copper atoms = Moles of copper * Avogadro's number
Number of copper atoms = 1.12 mol * 6.022 x 10^23 atoms/mol = 6.74 x 10^23 atoms

Number of silver atoms = Moles of silver * Avogadro's number
Number of silver atoms = 0.912 mol * 6.022 x 10^23 atoms/mol = 5.49 x 10^23 atoms

Comparing the two, we find that the copper bar has a greater number of atoms than the silver disk. The difference in the number of atoms is:
Difference in atoms = Number of copper atoms - Number of silver atoms
Difference in atoms = 6.74 x 10^23 atoms - 5.49 x 10^23 atoms = 1.25 x 10^23 atoms

Therefore, there are 1.25 x 10^23 more atoms in the copper bar than in the silver disk.

3) a) To find the number of moles of compound in the given mass of ammonium chloride, we will again use molar mass.

Given: Mass of ammonium chloride (NH4Cl) = 221 g, Molar mass of ammonium chloride = 53.49 g/mol.

Moles of ammonium chloride = Mass of compound / Molar mass of compound
Moles of ammonium chloride = 221 g / 53.49 g/mol = 4.13 mol

Therefore, there are approximately 4.13 moles of ammonium chloride in the given sample.

b) To find the number of moles of hydrogen in the sample, we need to consider the stoichiometry of the compound.

In ammonium chloride (NH4Cl), there are 4 hydrogen atoms per one molecule of NH4Cl.

Moles of hydrogen = Moles of ammonium chloride * (4 moles of hydrogen / 1 mole of NH4Cl)
Moles of hydrogen = 4.13 mol * (4 mol/1 mol) = 16.52 mol

Therefore, there are 16.52 moles of hydrogen in the given sample.

To summarize:
a) There are approximately 4.65 x 10^22 iron atoms in the given sample.
b) There are 0.07734 moles of iron in the given sample.

2) The copper bar has a greater number of atoms than the silver disk, with a difference of 1.25 x 10^23 atoms.

3) a) There are approximately 4.13 moles of ammonium chloride in the given sample.
b) There are 16.52 moles of hydrogen in the given sample.