26. During the titration of potassium hydrogen phthalate (KHP) with NaOH, why wa

Question

26. During the titration of potassium hydrogen phthalate (KHP) with NaOH, why was the phenolphthalein added to the flask? A. To catalyze the acid base reaction. B. To neutralize the acid base reaction C.To precipitate the acid base reaction D. As an indicator that turned pink, when there was excess acid E. As an indicator that turned pink, when there was excess basc. 27. In the Copper Lab, how did you know the reaction was complete? A. When the copper was dried in the oven B. When the blue color disappeared C. When aluminum no longer formed on the copper wire D. When the aluminum wire dissolved completely E. When the blue color formed 28. In a copper lab experiment, 1000 g of CuSO was dissolved in 600 ml of water and treated with a piece of aluminum wire. The resultant copper precipitate was filhered, dried and weighed. The mass of the copper was 0.369 g what is the % yield? A, 59.0 % 92.7% C.990% D.36.9 % E.X9% For questions 29-30: The following data was collected in an Ideal Gas Law experiment Mass of magnesium: 0.0513 g Volume of hydrochloric acid: 10.00 mL Molarity of hydrochloric acid: 2.0 M Atmospheric pressure: 723.5 mm Hg Temperature: 2 1.0 23.0 22.0 E 21.0 20.0 19.0 A. Magnesium is the limiting reactant and 0.00211 mol 18.0 Volume of gas produced: 25.0 mL 29. Which of the following statements is true? of magnesium chloride is formed mol of magnesium chloride is formed of magnesium chloride is formed magnesium chloride is formed magnesium chloride is formed 17.0 B. Magnesium is the limiting reactant and 0.00106 C. Magnesium is the limiting reactant and 0.00283 mol D. HCI is the limiting reactant and 0.00201 mol of 20.0 21.0 22.0 23.0 24.0 Temperature(c) E. HCI is the limiting reactant and 0.00125 mol of Using the graph of water vapor pressure, above right, what numerical value would be calcalated for 'R? D. 0.0174 4-atx E.0.440 mol K C. 0.08206 L B.0.01421a- mol k mol 1-a mol K A, 0.0374 nol K

Explanation / Answer

phenolpthalein indicator will be colorless in acidic solution it will turn basic when the solution become basic so it is used as a indicator to show when there is excess of base

Answer for 26 is (E) A indicator that will turn pink when there was excess base

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28)

Given mass of CuSO4 = 1 g

molar mass of CuSO4 = 159.61 g/mol

No. of moles of CuSO4 = mass / molar mass = 1 g / 159.61 g/mol = 6.26 * 10-3 mol will give 6.26 * 10-3 moles of Cu

Molar mass of Cu = 63.55 g/mol

Mass of Cu = No. of moles * molar mass = 6.26 * 10-3 mol * 63.55 g/mol = 0.398 g

Theoretical yield = 0.398 g

given actual yield = 0.369 g

% yield = actual yield / theoretical yield * 100 % = 0.369 g / 0.398 g * 100 % = 92.7 % Answer

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