Answer:
(between 6 and 7)
The answer submitted above is actually wrong. The correct answer for the following fruits would be:
Orange Juice - 4.35
Lemon Juice - 2.75
Grapefruit Juice- 3.65
Lime - 2.88
Here are some other common juices and their pH values from the USDA:
Apple Juice 3.35 - 4.00
Apricot Nectar 3.78
Grape Juice 3.4
Pineapple Juice, canned 3.30 - 3.60
Prune Juice 3.95 - 3.97
Guava nectar 5.50
All of these are approximates, different factors will produce different results, but should be close in range. The lower the numbers, the more acid, or acidic the juice is. The higher the number the more alkaline the juice is. The higher the better for your body. FYI: stomach acids' PH is 1.4.