CHEM-C125 ASSESSMENT TEST QUESTIONS WITH CORRECT ANSWERS CHEM-C125 ASSESSMENT TEST QUESTIONS WITH CORRECT ANSWERS

CHEM-C125 ASSESSMENT TEST QUESTIONS WITH CORRECT ANSWERS A solid sample contains both NaOH and NaCl. 0.500 g of this solid sample was dissolved in water to make a 20.0 mL solution and then this solution was titrated by 0.500 mol/L HCl solution. If 22.5 mL of HCl was used to reach the end point, what is the mass % of NaOH in the original solid sample? NaOH + HCl --> NaCl + H2O - Answer- 90 During titration, it is very common to have some NaOH spilled to the inside wall of Erlenmeyer flask. Ideally, these spilled NaOH should be washed down, but most students (if not all) did not do so. How will these NaOH on the wall affect the experimental result? a) Since these spills will make the volume of NaOH artificially higher, it will make the experimental result higher as well. b) Since these NaOH did not have a chance to react with acetic acid in vinegar, it will make the experimental result lower. c) Since these NaOH did not have a chance to react with acetic acid, it should not affect the experimental result. - Answer- a) Since these spills will make the volume of NaOH artificially higher, it will make the experimental result higher as well. A pressure gauge was used to measure the air pressure inside a tire. If the pressure gauge reads 27 psi, what is the real pressure in psi of air inside this tire? Assume atmospheric pressure is 15 psi. - Answer- 42 At constant pressure, density of gas is inversely proportional to its temperature. This is how hot air balloon is floating in air: burning fuel makes inside air temperature higher and density lower; low density air balloon float on high density regular air. What is the density of air in g/L at 50 degree C if the atmospheric pressure is 1.0 atm? The average molar mass of air is about 29 g/mol. Keep two decimal places for your answer. - Answer- 1.09 At STP, 0.106 g of a gas sample occupies a volume of 58.4 mL. What is the molar mass of this gas? Keep 3 sig figs for your final answer. - Answer- 40.7 Butane gas was collected in a graduated cylinder over water in Gas Laws lab. If the water vapor pressure at the given temperature is 2.4 kPa and the atmospheric pressure is 100.9 kPa, what is the pressure of butane in kPa inside the graduated cylinder? Keep one decimal place for your final answer. - Answer- 98.5 Use solubility rules from your textbook and/or lecture slides to answer the following question: