Hi Gretchen, I believe it does take 21 days to change or create a habit although I think the statement should be rephrased to say it takes approximately 21 days of consistent daily behaviour combined with belief, faith, determination and emotional leverage or sincere desire to succeed to form new habits.
An example of a weak acid is ethanoic acid. A weak acid has a pH of 3 to 5. ethanoic acid (in water) hydrogen ion + ethanoic ion CH3CO2H(aq) H+(aq) + CH3CO2-(aq) Some of the ethanoic acid molecules become ions in water but most of them stay as molecules. The reaction is reversible (shown by the arrow).
Quick Answer. One of the main differences between acids and bases is that acids have a pH that is less than 7 and bases have a pH that is greater than 7. When dissolved in water, acids are substances that will cause the concentration of hydrogen ions (H+) to increase.