Is this done correctly?

mass = 27.8 g CaCI2
Number of CaCI2 in the compound = (unknown)
Number of CI- ions in the compound = (unknown)
Number of moles = mass/molar mass
To find the number of moles of CaCI2 first you find the molar mass of the compound.
1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g
1 mole CI x 30.45 g CI/1 mole CI = 30.45 g
1 mole CI x 30.45 g CI/1 mole CI = 30.45 g
molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2
27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2
Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion
 =
1.204 x 10^23 CI- ions

 

38 minutes ago, Rachel Maddiee said:

1 mole CI x 30.45 g CI/1 mole CI = 30.45 g
1 mole CI x 30.45 g CI/1 mole CI = 30.45 g

Incorrect. Typo.

39 minutes ago, Rachel Maddiee said:

molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2
27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2

OK.

39 minutes ago, Rachel Maddiee said:

Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion
 =
1.204 x 10^23 CI- ions

Incorrect.

 

I can’t find the typo? And can you please tell me more specifically what is incorrect?

thank you!

11 minutes ago, Rachel Maddiee said:

I can’t find the typo? And can you please tell me more specifically what is incorrect!

In one line you entered the correct value, and one line later you entered wrong value.. Recheck them.

 

mass = 27.8 g CaCI2
Number of CaCI2 in the compound = (unknown)
Number of CI- ions in the compound = (unknown)
Number of moles = mass/molar mass
To find the number of moles of CaCI2 first you find the molar mass of the compound.
1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g
1 mole CI x 35.45 g CI/1 mole CI = 35.45 g
1 mole CI x 35.45 g CI/1 mole CI = 35.45 g
molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2
27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.25 mol CaCI2
Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion
 = 1.204 x 10^24 CI- ions
 

How is that?

Edited January 3, 20205 yr by Rachel Maddiee

54 minutes ago, Rachel Maddiee said:

Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion
 = 1.204 x 10^24 CI- ions

That's still wrong.. Actually wronger than previous..

What am I doing incorrectly? Am I missing a step?

OK I fixed it 

mass = 27.8 g CaCI2
Number of CaCI2 in the compound = (unknown)
Number of CI- ions in the compound = (unknown)
Number of moles = mass/molar mass
To find the number of moles of CaCI2 first you find the molar mass of the compound.
1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g
1 mole CI x 35.45 g CI/1 mole CI = 35.45 g
1 mole CI x 35.45 g CI/1 mole CI = 35.45 g
molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2
27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2

 0.250 mol CaCI2 x 6.02 x 10^23 formula units = 1.505 x 10^23 formula units CaCI2

1.505 x 10^23 x 2 CI- ions = 3.01 x 10^23 CI- ions

Generally good +1.

18 hours ago, Rachel Maddiee said:

27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2

With one yet another digit of precision it is 0.2505 mol

18 hours ago, Rachel Maddiee said:

 0.250 mol CaCI2 x 6.02 x 10^23 formula units = 1.505 x 10^23 formula units CaCI2

1.505 x 10^23 x 2 CI- ions = 3.01 x 10^23 CI- ions

With one more digit it will be 1.50852*10^23, and 3.017*10^23

But generally good answer.

 

Edited January 4, 20205 yr by Sensei