Question

For salt formation procedure crude lidocaine should be dissolved in diethyl ether and 2 ml of 2.2 M sulfuric acid should be added per each gram of solute. Calculate how many equivalents of sulfuric acid is taken to each equivalent of lidocaine. Round your answer to the whole number.

Answer 1

Answer:

20 equivalents of sulfuric acid are needed to per equivalent of lidocaine.

Explanation:

To do this calculation we should take in account the key information given:

2 mL (0.02 L) of sulfuric acid (H2SO4) 2.2 M per 1 g of lidocaine (molecular weight=234.34 g/mol)

So we can calculate from here the number of moles of each compound needed for the procedure.

Starting with the sulfuric acid, we know that the molar concentration is defined as [concentration] =n(moles number)/V(volume).

So n=[concentration]*V, and therefore :

n(H2SO4)=2.2 M * 0.02 L=0.044 mol

While the moles of lidocaine can be calculated as n(moles number)=m(mass amount)/mW(molecular weight), so:

n(lidocaine)=m(lidocaine)/mW(lidocaine)= 1 g /234,34 g/mol~0,0043 mol.

Now we can calculate the equivalents.

Take in account that for sulfuric acid, de number of equivalents per mole is 2 (because of the double dissociation of the acid), while the number of equivalents per mole of lidocaine is 1.

Then we can conclude that:

0,0043 equivalents of lidocaine need 0,088 equivalents of sulfuric acid

1 equivalent of lidocaine need (0,088/0.0043)=20,46~20 equivalents of sulfuric acid

Finally, we can conclude that for the described procedure, 20 equivalents of sulfuric acid per equivalent of lidocaine are needed.