. For each substance, find the pH from the given hydronium ion concentration.

(a) coffee, 1.26×?10?^(-5)

(b) milk, 2.51×?10?^(-7)

(c) lutefisk, 5.01×?10?^(-12)

(a) coffee, 1.26×?10?^(-5)

(b) milk, 2.51×?10?^(-7)

(c) lutefisk, 5.01×?10?^(-12)

## Comments

See http://www.usca.edu/chemistry/genchem/sigfig.htm; esp. “write the number in scientific notation. If you can/must get rid of the zeroes, then they are NOT significant.”

So the power of 10 part of a number in scientific notation does not contribute to the significant figures of the whole number.

My answers are correct.

^{-12}and compare to your answer to (c). Based on your rounding you would get the same pH value, which can't be.