what is the Ph of a solution whose hydronium ion concentration is 2.0 x 10(e-9)?

Question

what is the Ph of a solution whose hydronium ion concentration is 2.0 x 10(e-9) {neg. 9 exponent)M?
1) 12.6
2) 8.70
3) 9.30
4) 3.10

Answer 1

If it was 1x10(-9) it would be 9, so at 2x10(-9), it must be slightly more acidic so the answer is 8.70. You don't even need the calculator for this one.

Answer 2

Enter the hydronium concentration into your calculator. Push the "log" button and then change the sign from negative to positive.

pH is defined as the negative log of the hydronium ion concentration.

I'd suggest that you read your text and do your own homework.