At the other extreme, a 10 M solution of NaOH would have a pH of 15. Numerical examples from Shipman, Wilson and Todd. In pure water, the molar concentration of H + ions is 10-7 M and the concentration of OH-ions is also 10-7 M.
In order to tell if a guava is ripe, squeeze it gently. If it gives under your fingers, its ripe. 2. Look for any blemishes on the guava. You want to try to select guavas that are blemish-free. Blemishes or bruises can mean the fruit is bad or will not taste good. 3. Check the color of the guava. Ripe guavas are those that have gone from bright green to a softer yellowish-green color. If you see a touch of pink on the fruit, it is in its prime. If you don't find any that are yellow, you can always buy green guava and wait for them to ripen.
After purchasing a guava at the market, assuming it was ripe, taking it home and biting into a hard, bland fruit, I decided I needed to find out how to tell if one is ripe. After searching the internet I found these handy steps on how to find a juicy, sweet guava: Look at the color of the fruit.