What is the percent yield of the reaction? [Ans. : 43.21] 3) A 5.6780 gram sample of the compound Na2XO3 was dissolved in water then reacted with excess calcium chloride: Na2XO3(aq) + CaCl2(aq) →CaXO3(s) + 2NaCl(aq) A total of 5.4842 grams of CaXO3 were collected. What is the identity of the element “X?” [Ans. : Se, calculated molar mass 78.93 g] 4) A 0.3528 gram mixture of H2SO4 (molar mass 98 grams) and H3PO4 (molar mass 98 grams) was mixed with a little water and titrated with 9.70 mL of 1.000 M NaOH: 3NaOH(aq) + H3PO4(aq) →3H2O(l) + Na3PO4(aq) 2NaOH(aq) + H2SO4(aq) →2H2O(l) + Na2SO4(aq) What was the percent by mass H2SO4 in the original mixture?
To do this, first take the number of drops used to achieve the monolayer (1 drop) and convert it to mL using the calibrated number of drops per mL. Then multiply the number of grams of sodium stearate per milliliter of solution. Finally, convert to moles through the molar mass of sodium stearate. HINT: The molar mass of sodium stearate is 296.5 g/mole. Answer = 1.06*10^7 moles/top layer 5.
Repeat the titration until there are two titres within 0.1cm3 of each other. Record results in a suitable table. Results: Rough Titre: 7.653 First Run: 6.553 Second Run: 6.453 Third Run: 6.553 Calculations: During the titration, iron(II) ions are oxidised to iron(III) ions and manganate(VII) ions are reduced to manganese(II) ions. The equation is as follows: 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) ? 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) The above equation shows that one mole of manganate(VII) ions reacts with 5 moles of iron(II) ions in acid solution.
Lab 4: Determination of Percent by Mass of the Composition in a Mixture by Gravimetric Analysis Introduction Thermal gravimetric analysis is used to determine the percent by mass is used to determine the percent by mass of a component in a mixture. When a mixture is heated to an appropriately high temperature, one component in the mixture decomposes to form a gaseous compound. The mass of this particular component is related to the mass of the gaseous compound. In this experiment, the percent by mass of sodium hydrogen carbonate (NaHCO3) and potassium chloride (KCl) in a mixture will be determined. Experimental First, we weighed 2 samples, each has 1 gram of NaHCO3-KCl mixture Second, we put the samples in 2 crucibles (A and B) and weighed them.
* Trial 1 36-25.5=10g * Trial 2 36-25=11g * Trial 3 35.5-25=10g 2. Calculate the density of the unknown liquid for each trial. (Divide the mass of the liquid calculated above by the volume of the liquid.) * Trial 1: 10.5/50=0.20g/mL * Trial 2: 11/49=0.20 g/mL
IB HL Chemistry Energetics - End of Topic Test 35 min 37 marks Answer all the questions in the spaces provided 1. What energy changes occur when chemical bonds are formed and broken? A. Energy is absorbed when bonds are formed and when they are broken. B.
Where it resulted to values of 3.990602 x 10-3 s-1, 4.653278 x 10-3 s-1, 5.944044 x 10-3 s-1, 7.499958 x 10-3 s-1, 7.499958 x 10-3 s-1, 9.84554 x 10-3 s-1, for flasks 4, 5, 6, 7, 8. Then the Ionic strength was calculated using the equation µ=½∑ ci zi2 . Which resulted in 4.5392142 x 10-2, 6.4999998 x 10-2, 1.23823528 x 10-1, 2.21862742 x 10-1, and 4.17941175 x 10-1. It
UNIVERSITI TUNKU ABDUL RAHMAN Faculty Course Year/ Semester Session : : : : Faculty of Science Bac. of Science (Hons) Chemistry Year 3 Semester 1 201105 or May 2011 Unit Code Unit Title Lecturer Assignment : : : : UDEC3254 Spectroscopy and Chromatography II Dr. Lim Chan Kiang 2 Answer all questions 1. A mixture of steroid hormones consisting of cortisone, cortexone and corticosterone was separated using a HPLC silica column eluted with a binary mixture of acetone and hexane (20:80). (i) What is the order of elution time for the above compounds from the HPLC column? (3 marks) (ii) What is the chromatographic mechanism involved?
(b) Calculate the volume of 0.2M UO3- needed to react with 20.00 cm3 of 0.1M Cr2O72-. 3. 24.40 g of hydrated iron(II) sulphate, FeSO4.xH2O was dissolved and made up to 1.0 dm3 of aqueous solution, acidified with sulphuric acid. 25.00 cm3 of the solution was titrated with 20.00 cm3 of 0.022M potassium manganate(VII) solution for complete oxidation. a) Write the equation for the reaction.
Through these calculations, the concentration of hydrochloric acid was found to be 8.3 mol•L-1. Purpose Refer to handout “Standardize an Approximately 1 mol•L-1 Hydrochloric Acid” Material and Method Refer to handout “Standardize an Approximately 1 mol•L-1 Hydrochloric Acid” Results Quantitative Results Trial Initial Final Reading (in mL) Volume HCl Used (in mL) 1 0.2 12.4 12.2 2 12.4 23.9 11.5 3 23.9 36.3 12.4 Calculations Average volume of HCl