Chapter 25
Chemical Principles in the Laboratory · 3 exercises
Problem 1
A solution of a weak acid was tested with the indicators used in this experiment. The colors observed were as follows: \(\begin{array}{llll}\text { Methyl violet } & \text { violet } & \text { Congo red } & \text { violet } \\ \text { Thymol blue } & \text { yellow } & \text { Bromcresol green } & \text { yellow } \\ \text { Methyl yellow } & \text { orange } & & \end{array}\) What is the approximate \(\mathrm{pH}\) of the solution? _______________
6 step solution
Problem 2
An aqueous solution of \(\mathrm{NH}_{3}\) has a pH of \(11.6 .\) The ammonia \(\left(\mathrm{NH}_{3}\right)\) molecule is the conjugate base of the \(\mathrm{NH}_{4}^{+}\) (called "ammonium") ion. Write the net ionic equation for the reaction that makes an aqueous solution of \(\mathrm{NH}_{3}\) basic. (Eq. 5.).
5 step solution
Problem 3
The pH of a 0.10 MHOBr solution is 4.8. a. What is \(\left[\mathrm{H}^{+}\right]\) in that solution? ______________M b. What is \(\left[\mathrm{OBr}^{-}\right] ?\) What is [HOBr]? (Where do the \(\mathrm{H}^{+}\) and \(\mathrm{OBr}^{-}\) ions come from?) ________________M;_________________M c. What is the value of \(K_{\mathrm{a}}\) for HOBr? What is the value of \(\mathrm{p} K_{\mathrm{a}} ?\) _____________ ___________________.
3 step solution