how to free memory

[kfaday]

I've got a char array

char *vec;

and i allocate memory for a number of elemets

vec = (char*) malloc ((sizeof(char))*(number_of_elemets));

i do that in main.
then i call a free function

free_mem (vec);

the function code is:

void free_mem (char *vec,number_of _elements)
{   
        for (i=0;i<(number_of _elements);i++)
	{
                 	free (vec[i]);
	}
}

it gives me errors
what's wrong?
thanks!!