Question

12. a sample of silver with a mass of 8.44g reacts with sulfur to form a compound that has a mass of 9.6g, what is the percent composition of the compound?

15. a sample was found to contain 1.062g hydrogen, 133.757g of iodine and 50.589g of oxygen. The mass of the compound is 175.91g/mol. What is the molecular formula?

17. how many moles of oxygen (O2) are contained in a 5.0 L cylinder that has a pressure of 175 atm and a temperature of 20 degrees Celsius? (ideal gas law)

Answer 1

12)

In compound:

% silver = mass of silver * 100 / mass of compound

= 8.44*100/9.6

= 87.9 %

% sulfur = 100 - 87.9

= 12.1 %

13)

we have mass of each elements as:

H: 1.062 g

I: 133.757 g

O: 50.589 g

Divide by molar mass to get number of moles of each:

H: 1.062/1.008 = 1.0536

I: 133.757/126.9 = 1.054

O: 50.589/16.0 = 3.1618

Divide by smallest to get simplest whole number ratio:

H: 1.0536/1.0536 = 1

I: 1.054/1.0536 = 1

O: 3.1618/1.0536 = 3

  

So empirical formula is:HIO3

Molar mass of HIO3,

MM = 1*MM(H) + 1*MM(I) + 3*MM(O)

= 1*1.008 + 1*126.9 + 3*16.0

= 175.908 g/mol

Now we have:

Molar mass = 175.91 g/mol

Empirical formula mass = 175.908 g/mol

Multiplying factor = molar mass / empirical formula mass

= 175.91/175.908

= 1

So molecular formula is:HIO3

Answer: HIO3

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