## Frostbite one year ago Activity and pH

1. Frostbite

The true definition of pH is: $\Large pH = -\log(a_{\sf H^{+}})$ Where $$a_{\sf H^{+}}$$ is the activity of protons in aqueous solution. We usually approximate that equation with the following expression: $\Large pH = -\log(m_{\sf H^{+}})$ Where $$m_{\sf H^{+}}$$ is the molality of protons in the aqueous solution. In question we shall be looking at how good this approximation is by using Debye­-Hückel theory to evaluate the pH of a aqueous solution of hydrochloric acid. a) Using the approximation expression of pH, calculate the pH of a 0.40 molal aqueous solution of hydrochloric acid. b) In the lab I was measuring the pH of a 0.40 molal aqueous solution of hydrochloric acid as accurately I could to 0.52 at 25 $$^{\circ}$$C. Calculate the activity coefficient for $$\sf H^{+}$$ HINT: $$\gamma_{H^{+}}=\gamma_{\pm}$$ c) Calculate the activity coefficient using the simple Debye­-Hückel equation for a 0.40 molal hydrochloric acid solution. d) Using the measured activity coefficient from b), calculate the $$B$$ factor using the extended Debye­-Hückel equation (assume that $$C=0$$) e) Using the $$B$$ factor and the extended Debye­-Hückel equation, calculate the pH for a 1.0 molal HCL solution. Did the result fit your expectations and why?

2. arindameducationusc

Are we going to get the solutions?