A sample of a certain organic acid has a mass of 5.000 g. Elemental analysis of this compound found it to contain 1.334 g C, 3.554 g O, and the rest of the mass is hydrogen. If the molar mass of the organic acid is 90.03 g/mol, determine its molecular formula.

C₂H₂O₄

Explanation:

Given parameters:

Mass of organic acid  = 5g

Mass of C  = 1.334g

Mass of O = 3.554g

Mass of H = 5  - (1.334 + 3.554)  = 0.112g

Molar mass  = 90.03g/mol

Unknown:

Molecular formula of the compound  = ?

Solution:

To solve this problem, we find the empirical formula of the compound first. It is the simplest formula of the compound.

Elements                        C                     H                        O

Mass                             1.334               0.112                   3.554

Molar mass                       12                   1                          16

Number of moles          1.334/12          0.112/1                 3.554/16

                                         0.112              0.112                     0.222

Divide by the

Smallest                         0.112/0.112        0.112/0.112          0.222/0.112

                                                1                       1                      2

           Empirical formula  = CHO₂  

The molar mass of this empirical formula  = 12 + 1 + 2(16) = 45g/mol

Now;

  Multiplication index  =    = 2

Molecular formula  =  (CHO₂)₂    = C₂H₂O₄  

he uptake of drugs from the intestine is often strongly influenced by diffusion. for example, consider a water-insoluble steroid for treating inflammation that is solubilized in aggregates of detergent molecules, called micelles. these micelles, aggregates of 80 soap molecules, have a molecular weight of 24,000, a diameter of 2.6 nm, and a charge of -27. the positively charge ions (counterions) in this system are na".

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.