C125 Final Lab-Simple

If you accidentally spilled some dilute HNO3 on the ground, what should you do? - Answer- Use excessive NaHCO3 to neutralize it and then clean it. Random errors may affect the... - Answer- precision but not the accuracy. Phenolphthalein is the pH indicator used in Vinegar Analysis lab. Which one of the following solutions may turn pink if a few drops of phenolphthalein is added? - Answer- 10 mL of a 0.20M HCL solution combined with 15 mL of 0.20M NaOH solution A balance always reads 0.1g higher. If this balance is used in Gas Law lab to determine the molar mass of butane, how will this systematic error affect the result? - Answer- Since the mass difference is used, this systematic error will be canceled in the subtraction. As a result, it should not affect the experimental result. When copper wire is immersed into a silver nitrate solution, the original colorless solution becomes light blue. What substance or ion is causing this blue color? - Answer- Cu2+ ion What will increase the purity of compound in crystallization? - Answer- Settle it down in the drawer and let the solution cool down slowly so that large crystals are formed slowly. What might increase as a result from increasing concentration in a solution? - Answer- absorbance How should the % purity be reported with the correct number of significant figures? - Answer- 92 +/- 3% In a hydrogen atom, which principle quantum number is for the ground state of electron? - Answer- n=1 Which statistical value is used to measure how well your results fit a linear relationship? - Answer- R^2 In Beer Lambert Law, A=ebc. b stands for... - Answer- path length Which one of the following is the most energetic transition in a hydrogen atom? - Answer- n=1 to n=5 The degree to which the experimental result is to the established literature value is called... - Answer- accuracy What represents the precision of a set of measurements? - Answer- standard deviation At constant pressure, the volume of a gas is directly proportional to its absolute temperature. This is a statement of... - Answer- Charles's Law strong electrolyte - Answer- soluble ionic compounds and strong acids What is the driving force for the reaction between CO2 and NaOH in an aqueous solution? - Answer- neutralization When a colorless NaOH solution is mixed with a colorless HCl solution, what will happen? - Answer- There is no visible change, though a chemical reaction occurs. A test tube has a colorless aqueous layer of NaI solution and an colorless organic layer of methylene chloride. When a few mL of colorless chlorine water is added to this test tube, the organic layer becomes pink. What is causing this pink color in the organic layer? - Answer- I2 Evaporation of water... - Answer- is endothermic and has a positive enthalpy change. Which of the following orbitals of H has the lowest energy? - Answer- 2s and 2p What is directly proportional to the concentration of a solution sample? - Answer- absorbance of light When measuring the transmittance of the Fe standard solution, what is used as blank? - Answer- DI water When intensity of light changes due to sample absorption, which of the following change accordingly? - Answer- transmittance According to VSEPR theory, molecules generally adopt a structure that... - Answer- separate electron pairs as far away from others as possible around the central atom of the molecule. Which of the following is/are the possible methods of deciding which atom in the CN- ion has more negative charge? - Answer- Determine the formal charge of each atom in the ion, and determine which atom is more electronegative. Which one is correct about the bond lengths in PCl5? - Answer- Axial bonds are longer because they experience higher repulsion. Draw the best Lewis structure of N2O and consider resonance structures if there are any. What is the bond order between the two N atoms in N2O? - Answer- More than 2 but less than 3.