Create a new dataset which displays the 'mean' for each column

I have a dataframe that looks like this:

and i want to create a function which iterates through 'C', 'H', 'E', 'G', 'D', and creates a new dataframes where the row values are replaced with the mean, eg: meanC = 33/25, meanH = 45/25, meanE = 23/25.

I am not quite sure how to go about it.Any help would be appreciated, thankyou!