C125 - Study guides, Class notes & Summaries

C125 MIDTERM REVISION EXAM QUESTIONS WITH CORRECT ANSWERS A student experimentally determined the mass % compisition of Ca in CaCO3 to be 38.9%. What is the real mass % composition of CaCO3? What is the % error? - Answer- real = 40.04% error = 2.858% Recall the procedure (chemical measurements). How would the following source of errors affect calculated density of water? A balance was improperly calibrated and always weigh masses 1.0g less than the real masses - Answer- no effect (take...

C125 EXAM REVIEW QUESTIONS WITH CORRECT ANSWERS Red and purple are two lines of hydrogen lamp. Which one is correct when comparing these two lines? - Answer- -Red line has smaller energy than the purple one -Red line has longer wavelength than the purple one According to Bohr's Model, which one is correct about a transition from n=2 to n=1 in a hydrogen atom? - Answer- It is a transition from an excited state to a ground state The lines observed in H-lamp are parts of Balmer Series. ...

C125 REVISION EXAM QUESTIONS WITH COMPETE SOLUTIONS In the molar mass lab, why was it important to level the water in the graduated cylinder with that in the through? - Answer- so that the pressure inside the cylinder would equal atmospheric pressure butane hazards - Answer- butane lighter fluid is extremely flammable. it is a mixture of two isomers both of which boil at temperatures below 0°C at 1 atm pressure. the gas is stored as a liquid in the pressurized container. However, when th...

In Atomic Spectra lab, Vernier angles (V) in degrees of a Hg-lamp has a linear dependence on wavelength (λ) in nm of line spectra: V = 0.146 λ−10.85 a) Predict the Vernier angle in degree for a line that has a wavelength of 510 nm. b) If a student found a line at a Vernier angle of 76.5°, what is the wavelength in nm of this line? - Answer- a) 63.61 b) 598.288 Best-fit line equation commonly takes "y=mx+b" format. What are y, x, m and b? - Answer- y = y-value x= x-value m = slope ...

If we apply the HOMO and LUMO concepts in atomic orbitals, we will have HOAO (Highest Occupied Atomic Orbitals) and LUAO (Lowest Unoccupied Atomic Orbitals). What is the LUAO of Na atom? - Answer- 3p Which one is correct about the bond lengths in PCl5? Equatorial bonds are longer because they experience smaller repulsion The axial bonds are shorter because they are far away from other bonds All P-Cl bonds have the same bond length. Axial bonds are longer because they experienc...

C125 MIDTERM EXAM QUESTIONS AND ASWERS If 11.3 g of NaCl is dissolved in 100. g of water, what is the percent by mass (mass%) concentration of NaCl in the solution? Note: 1. Use three sig figs for your final answer. 2. Do not enter your answer as fractions. For example, if you think 30% is the correct answer, enter either "30" or "30%". Do NOT enter "0.30". - Answer- 10.2 How many moles of NaOH will be needed to neutralize 0.86 mol of H2SO4? The following equation is NON-bal...

C125 FINAL EXAM QUESTIONS AND ANSWERS

PCl5 - Answer- All of the following molecules have all bonds being equivalent except: SF6 CH4 NH3 PCl5 lone pair to lone pair - Answer- Which of the following has the largest repulsion, assuming that all the angles between electron pairs are identical? -They are all the same because they all contain the same number of electrons -lone pair to lone pair - bonding to bonding pair -lone pair to bonding pair square planar - Answer- What is the molecular geometry of XeF4? none of ...

Rearrange the following equation to solve for P. (P+a)(V-b)=nRT - Answer- P=(nRT/V-b) -a What is the slope if B is plotted on y-axis and A is plotted on x-axis? 5A + 3B = 8 - Answer- -5/3 In an experiemnt, the best-fit-line equation between Absorbance (A, unitless) and concentration (c, mg/mL) is used to calculate the concentration of Fe. Based on the best-fit line equation given below, what is the concentration of Fe if the absorbance is 1.25? A = 851 c + 0.03 - Answer- 0.0014 ...

Aliquot - Answer- - *Portion of measurement added* - Example: "In this experiment, we will be using an *aliquot* of 10 mL of water for each trial Sig Fig Rules (Significant) - Answer- - Any non-zero digit is a sig fig - Zeros between non-zeros are sig figs - Zeros to the right of the last non-zero digit are sig figs Sig Fig Rules (Insignificant) - Answer- - Zeros to the left of the first non-zero are NOT sig figs Calculations Rules for Sig Figs (+/-) - Answer- - Focus on decim...