Itachi S.

# Chemistry with stoichiometry and empirical formula

A compound that does not contain oxygen is combusted to give: a) 33.75 g of water b) Carbon dioxide collected under water in a 37.5 L vessel at 20 degrees Celsius and an atmospheric pressure of 752.2 torr. c) Sulfur dioxide which is collected by dissolution in water. This aqueous solution is titrated (reacted) with a 1.85M solution of sodium hydroxide. To reach the equivalency point, 404.5 mL of NaOH solution were consumed.

The vapor pressure of P(H2O)= 17.5 mmHg @20.0 Degrees Celsius.

The equivalency point is when enough base was added to consume all the acid present.

1. Determine the molecular formula of the compound if the molar mas of the compound is 179 g/mol as determined by the mass spectrometry.

2. Write a balanced equation for the combustion reaction and the titration.

3. Calculate the volume (L) of oxygen at STP needed for the combustion of 120 g of this compound.

If you can even just answer a part of this, it would be greatly appreciated!

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5.0 (641)

Steve C. Math & Chemistry Tutoring

Itachi S.

Thank you so much! I just wanted to clarify:

The pressure must be corrected for the vapor pressure of water (Dalton's Law of partial pressure).

What does that mean?

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09/21/15

Steve C.

When you collect the carbon dioxide by water displacement, part of the pressure of the gas in the container will be due to the presence of water vapor.  To find the pressure due to carbon dioxide, subtract the water vapor pressure from the total atmospheric pressure given.
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09/22/15

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