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titrated with a 0.200 M solution of the base, LiOH. Write the balanced chemical reaction for neutralization reaction: HClO4 (aq) + LiOH (aq) → LiClO4 (aq) + H2O (l) Write the NET ionic equation for the neutralization reaction. OH⁻ (aq) + H⁺ (aq) → H2O (l) Compute the pH of the titration solution. Show your work i) before any of the base is added ii) after 25. mL of base is added iii) after 50. mL of base is added A student performs the titration with the same chemicals but with smaller volumes of each chemical . Which of the following titration curves could represent the titration. Explain A because this entails a strong acid and a strong base. Question 2 A student performs a titration of an unknown acid with a strong base and gets the following titration curve: a) The student consults the list of pKa of acids shown below. If the acid is listed in the table below, which is the most likely identity of the unknown acid? Explain. Acid Ka HF 7.2 x 10-4 CH3COOH 1.8 x 10-5 H2CO3 4.3 x 10-7 HBrO 2.0 x 10-9 The unknown acid is HBrO because the calculated Ka is in between 50^-4 and 50^-6 and 2.0 x 10^-9 lies in between them. b) What is the initial molarity of the acid? 10^-3 = 0.001M Question 3 a) Describe the components and the composition of an effective buffer solution. Explain how the components of the buffer allow the buffer to maintain its pH. An effective buffer solution has a weak acid and its conjugate base or a weak base and its conjugate acid. A buffer solution is most effective when the ratio of its component concentrations is close to 1, also when the pH is equal to the pka of the acid.; The components of the buffer allow the buffer to maintain its pH because buffers can absorb excess H+ions or OH– ions. An employer is interviewing four applicants for a job as a laboratory technician and asks each how to prepare a buffer solution with a pH of 5.0. The following constants may be helpful: hydrazoic acid, pKa = 4.74 Boric acid, pKa = 9.23 Archita A. says she would mix equal molar solutions of hydrazoic (HN3) and sodium azide (NaN3) solutions. Bradley B. says she would mix equimolar Boric acid (H3BO3) and HCl solutions. Carlos C. says he would mix equimolar Boric Acid (H3BO3) and sodium dihydrogen borate (NaH2BO3) solutions. Delia D. says he would mix equimolar hydrazoic Acid (HN3) and NaOH solutions. b) Which of these applicants has given an appropriate procedure? Explain your answer Delia because she is using Sodium hydroxide which results in a pH of 5. NaOH is a strong base and in order to have an effective buffer a weak acid must be incorporated which is the HN3. c) Explain what is wrong with the erroneous procedures. The rest all incorporate a strong acid and a strong base or a weak acid and a weak base which don’ result in an effective buffer. d) The applicants have access to the 1 Liter volumes of each of the solutions listed above. They have access to graduated cylinders. In order to make 1.0 Liter of the correct 5.0 buffer solution, what volumes of the two chemicals must be mixed?

units. Chemical Equation: Write a generic chemical equation for the dehydration of cobalt (II) chloride ∙ x hydrate (include the state symbols of the reactant and two products). [T2] Mass of Reactants and Products: a) Calculate the initial mass of the hydrated cobalt (II) chloride. [T1] b) Calculate the final mass of the anhydrous cobalt (II) chloride remaining in the cruiio8icible. [T1] c) Calculate the mass of water given off by the sample of hydrated cobalt (II) chloride. [T1] Moles of Products: a) Calculate the moles of anhydrous cobalt (II) chloride remaining in the crucible. [T1] b) Calculate the moles of water released from the hydrate. {T1] 4. Mole Ratio a) Create an experimental mole ratio between the b) and a). [T1] 5. Formula of Hydrate: State the chemical formula you have determined for this hydrate. Round the formula to the closest whole number value for x. [T1] Discussion/Conclusion Questions: [T6] Based on the chemical formula of the hydrate, calculate the percentage composition (percent by mass) of the hydrated cobalt (II) chloride. Remember to determine the percentage of each element (Co, Cl, H, and O). [T2] A possible source of systematic error in this experiment is insufficient heating. Suppose that the hydrate was not completely converted to the anhydrous form. Describe how this would affect: the calculated percent by mass of water and the experimental molecular formula (i.e. would x be higher, lower or the same). Suppose a student spilled some of the hydrated cobalt (II) chloride. Describe how this would affect the calculated percent by mass of water (would it be higher, lower or the same) and the experimental chemical formula of the hydrate. [T2]

SWER TO EACH QUESTION ON THE APPROPRIATE LINE ON THE ANSWER SHEET. FOR OTHER QUESTIONS, CLEARLY WRITE THE ANSWER, INCLUDING UNITS WHEN NECESSARY, ON THE ANSWER SHEET. SHOW ALL WORK ON A SEPARATE SHEET OF PAPER. HAND IN ASSIGNMENT, ANSWER SHEET, AND SCRAP WORK. 1. How many valence electrons are expected for an element that is in group 15/5A of the periodic table? A. two B. three C. five D. eight E. ten 2. Which of the following pairs of bonded atoms would be expected to have the longest bond length? A. C  N B. C  S C. C  B D. C  Fsdfasdfas

SWER TO EACH QUESTION ON THE APPROPRIATE LINE ON THE ANSWER SHEET. FOR OTHER QUESTIONS, CLEARLY WRITE THE ANSWER, INCLUDING UNITS WHEN NECESSARY, ON THE ANSWER SHEET. SHOW ALL WORK ON A SEPARATE SHEET OF PAPER. HAND IN ASSIGNMENT, ANSWER SHEET, AND SCRAP WORK. 1. How many valence electrons are expected for an element that is in group 15/5A of the periodic table? A. two B. three asdf

SWER TO EACH QUESTION ON THE APPROPRIATE LINE ON THE ANSWER SHEET. FOR OTHER QUESTIONS, CLEARLY WRITE THE ANSWER, INCLUDING UNITS WHEN NECESSARY, ON THE ANSWER SHEET. SHOW ALL WORK ON A SEPARATE SHEET OF PAPER. HAND IN ASSIGNMENT, ANSWER SHEET, AND SCRAP WORK. 1. How many valence electrons are expected for an element that is in group 15/5A of the periodic table? A. two B. three dfgdsfgadsfas

TING THE BEST ANSWER TO EACH QUESTION ON THE APPROPRIATE LINE ON THE ANSWER SHEET. FOR OTHER QUESTIONS, CLEARLY WRITE THE ANSWER, INCLUDING UNITS WHEN NECESSARY, ON THE ANSWER SHEET. SHOW ALL WORK ON A SEPARATE SHEET OF PAPER. HAND IN ASSIGNMENT, ANSWER SHEET, AND SCRAP WORK. 1. How many valence electrons are expected for an element that is in group 15/5A of the perio