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11 Dec 2019

A 0.5131 g solid sample containing a mixture of LaCl3 (molar mass = 245.26 g/mol) and Ce(NO3)3 (molar mass = 326.13 g/mol) was dissolved in water. The solution was titrated with KIO3, producing the precipitates La(IO3)3(s) and Ce(IO3)3(s). For the complete titration of both La3 and Ce3 , 43.73 mL of 0.1228 M KIO3 was required. Calculate the mass fraction of La (your answer should have the units g La/ g sample) and Ce (your answer should have the units g Ce/ g sample) in the sample. Please show work

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Nestor RutherfordLv2

13 Dec 2019

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Easy questions. Please help. Question 3 to 12.

Now that we understand the basics. Snape wants you to consider the following UNBALANCED equation: Al(s) + HCl (aq) rightarrow AlCl_3(aq)+H_2(g). Assume you have plenty of HC1 and 6.0 mole of Al. How many moles of H_2 are formed? Express your answer in moles. Let's try one more but add the theoretical yield concept. Consider the following UNBALANCED equation: NO(g) + H_2(g) rightarrow NH_3(g) + H_2O(g) If you start with 89.3 g NO(g) and 28.6 g H_2(g), find the theoretical yield of ammonia. Express your answer in grams. Ron Wesley isn't the best experimentalist. After an experiment, he ends up with only 3.10 g of product. However, the same reaction has is a theoretical yield of 3.50 grams of product. What is the percent yield? in attempts to lift Ron's spirits, Dumbledore asks him a fairly easy question: calculate the mass percent composition of carbon in C_2H_5Cl. Prof. Vitarelli thinks you should try this also. Ron was able to get the previous problem right! Hopefully so were you. Now, as a small extension to the previous problem Snape asks everyone to calculate the mass of chlorine in 21 kg of C_2F_3Cl_3. Express your answer in kg. Looking at the bottom of her tea cup, Prof. Trelawney suddenly has a revelation! She knows one of the previous exam questions! She bursts into the class and yells: Analysis of a sample is finds it contains 15.0% of species X, by mass. 75.0% of species Y, and 10.0% of species Z, by mass. the molar mass of species X is 45.0 g/mole, the molar mass of species Y is 150. g/mole, and the molar mass of species Z is 30.0 g/mol. If the molar mass of the sample is 1200 g/mole, what is the molecular formula of the sample? Prof. Vitarelli frowns at her disapprovingly. X_4Y_6Z_4 X_4Y_5Z_4 X_3Y_6Z_3 X_4Y_4Z_4 X_2Y_5Z_2 As a final problem for the week Snape thinks we should incorporate something from a previous week, hydrates perhaps. Suppose we have a compound that is 4.330 % Li, 22.10 % Cl, 39.89 % O, and 33.69 % H_2O. What is the compounds formula? LiClO_4 middot 3 H_2O LiCl_2O_3, middot 5 H_2O Li_2Cl_2O_3 middot 5 H_2O Li_2Cl_2O_3 middot 4 H_2O LiClO_3 middot 4 H_2O

n this exercise, weighed samples of a solid unknown containing NaCl and NaHCO3 react with hydrochloric acid. The volume of the CO2 liberated by the reaction in the gas phase is measured with a gas collection syringe. From the volume we can calculate the number of moles of CO2 in the gas phase using the ideal gas approximation.

Since the CO2 is generated in an aqueous environment (aqueous HCl), some CO2 will dissolve in the liquid phase. The amount of CO2 dissolved in the liquid phase is computed using Henry's Law which requires knowing the partial pressure of CO2. As described in the exercise, this requires knowing the volume of the entire gas system ( VfTOT)

To insure that your answers agree with Mr. OSCER's, use the values in the below table for the basic constants required. .

	Value	Units
Ideal Gas Constant	0.0821	L-atm/mol K
Convert Celsius temperture to Kelvin	273.15	K
Atmospheric Pressure	760.0	Torr
Molar Mass of NaHCO3	84.01	g/mol
Henry's Law Constant for CO2 in water	3.2 X 10-2	mmol/mL-atm

The figure below illustrates the volumes that are designated by Vtube and Vsyr .

Note also that Vsyr = Vf â Vi .

The table below contains data collected for one run of the required reaction, where an unknown sample mixture containing some NaHCO3 is mixed with hydrochloric acid:

	Value	Units
Initial Weight of container (empty)	18.4395	g
Final Weight of container and unknown	18.6185	g
Volume of hydrochloric acid	10.0	mL
Volume of tube, V_tube (see Figure above)	92.3	mL
Initial volume of syringe (V_i)	5.0	mL
Final volume of syringe (V_f)	50.7	mL
Temperature	26.5	^oC
Atmospheric Pressure	764.4	Torr
Vapor Pressure of Water at 26.5 ^oC	25.8	Torr

Use this data to answer the following questions. The appropriate units are specified in the each question. Pay close attention to the number of significant figures in your answers.

weight of sample (g) mixture before the start of the reaction = .179 g. Volume of CO2 gas (mL) that is produced by the reaction and is now contained in the syringe= 45.7 mL

What mass (g) of NaHCO₃ was contained in the sample mixture that was mixed with HCl ?

Enter a numeric answer only, to the correct number of significant figures. Do not include units with your answer.

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