Chemistry, 22.10.2019 00:50, ylianafghgfdsnm1479
The ka of hydrofluoric acid (hf) at 25.0 degrees celsius is 6.8*10-4. what is the ph of a 0.15m aqueous solution of hf? the ka of hydrofluoric acid (hf) at 25.0 c is 6.8 x10-4. what is the ph of a 0.15 m aqueous 8) solution of hf? a) 4.60 b) 0.82 c)3.64 d) 1.17 e) 2.00
Answers: 3
![K_{\text{a}} = \dfrac{\text{[H}_{3}\text{O}^{+}] \text{F}^{-}]} {\text{[HF]}} = 6.8 \times 10^{-4}\\\\\dfrac{x^{2}}{0.15 - x} = 6.8 \times 10^{4}\\\\\text{Check for negligibility of }x\\\\\dfrac{ 0.15 }{6.8 \times 10^{-4}} = 220 < 400\\\\\therefore x \text{ is not negligible. We must solve a quadratic.}](/tpl/images/0339/7189/18f64.png)
![x^{2} = 6.8 \times 10^{-4} (0.15 - x)\\x^{2} = 1.02 \times 10^{-4} - 6.8 \times 10^{-4}x\\x^{2} + 6.8 \times 10^{-4}x - 1.02 \times 10^{-4} = 0\\\text{Solve the quadratic and get}\\x = 9.77 \times 10^{-3}\\\rm [H_{3}O^{+}]= x \, mol \cdot L^{-1} = 9.77 \times 10^{-3} \, mol\cdot L^{-1}](/tpl/images/0339/7189/cdff9.png)
![\text{pH} = -\log{\rm[H_{3}O^{+}]} = -\log{9.77 \times 10^{-4}} = \boxed{\mathbf{2.01}}](/tpl/images/0339/7189/8cf13.png)
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The ka of hydrofluoric acid (hf) at 25.0 degrees celsius is 6.8*10-4. what is the ph of a 0.15m aque...
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