Certified Reference Material (CRM), GSS-5, is certified to contain 40.67 ± 3.33 mg/kg of Ni in soil. An analysis of the CRM gives values of 40.39, 41.98, 43.64, 44.38, and 45.96 mg/kg. Determine the tcalc. value and determine if your results differ from the expected results at the 90 % confidence level?

Before investigating the scene, the technician must dilute the luminol solution to a concentration of 2.00x10-2 M. The diluted solution is then placed in a spray bottle for application on the desired surfaces. How many moles of luminol are present in 2.00 L of the diluted spray? Express your answer with the appropriate units.

If you use [KMnO4]=0.0252 M, Concentration of FeSO4 7 H2O = 5.70 g/L Using a 100-mL graduated cylinder, 50 mL sample of FeSO4*7 H₂O will be measured out. To each sample of FeSO4 7 H2O, add 10.0 mL of H2SO4 and 10 mL of H3PO4 Concentration of SnCl2 2 H2O 2.85 g/mL Using a 100-mL graduated cylinder, 50.0 mL sample of SnCl2 2 H₂O will be measured out. No additional acid is needed. #1 KMnO4 #1 KMnO4 Sample # Initial buret, mL Final buret, mL FeSO4*7 H2O 12.05 21.51 SnCl2 2 H₂O 0.07 9.54 Question) Answer the following questions. b) Determine mol of electron lost per mol of Sn ion. 1) In this case, your answer should be in decimal notation (for example, 0.123, not 1.23*10^-1) with the correct number of significant figures. Also follow the unit specified in each question. Do NOT put its unit in your answer because its unit is shown already in the questions.

A student determines the concentration of an unknown sample using two different methods. Each method has three different trials; the average, standard deviation, and percent error produced by each method is listed below. Method 1 Average: 10.56 M NaOH Standard deviation: 1.35 M NaOH Percent error: 1.25% Method 2 Average: 10.92 M NaOH Standard deviation: 1.02 M NaOH Percent error: 3.45% Which method was more accurate? How can you tell?