For the majority of minerals, the streak obtained when the mineral is scratched against a porcelain plate is a. only useful if the mineral is softer than the porcelain streak plate. b. always dark brown or black. c. always diagnostic of that mineral. d. not useful, because the porcelain will often chemically react with the mineral.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

it would be d. henry moseley

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