Question

In: Chemistry

A sample containing a mixture of SrCl2·6H2O (MW = 266.62 g/mol) and CsCl (MW = 168.36...

A sample containing a mixture of SrCl2·6H2O (MW = 266.62 g/mol) and CsCl (MW = 168.36 g/mol) originally weighs 1.7215 g. Upon heating the sample to 320 °C, the waters of hydration are driven off SrCl2·6H2O, leaving the anhydrous SrCl2. After cooling the sample in a desiccator, it has a mass of 1.2521 g. Calculate the weight percent of Sr, Cs, and Cl in the original sample.

Expert Solution

Weight of sample with water of hydration = 1.7215 grams

Weight of sample after water of hydration is removed = 1.2521 grams

Amount water present as water of hydration = 1.7215-1.2521 = 0.4694 grams

Molar mass of water =18 grams/mole

Molecular weight of water = 0.4694 /18 = 0.026078 moles

Now 1 mole SrCl₂.6H₂O = 6 Moles of H₂O

Therefore, moles of SrCl₂.6H₂O present in 0.026078 moles of H₂O =(1/6)*0.026078 = 0.004346 moles

moles of SrCl₂.6H₂O = 0.004346 moles

Molar mass of SrCl₂.6H₂O = 266.62 grams/mole

Weight of SrCl₂.6H₂O =0.004346 *266.62 =1.15873 grams

Now consider SrCl₂.6H₂O,

1 mole Sr = 1 mole SrCl₂.6H₂O

Therefore of Sr =0.004346 mole

Molar mass of Sr =87.62 grams/mole

Weight of Sr = 0.004346 *87.62 = 0.380826 grams

2 moles of CL = 1 mole of SrCl₂.6H₂O

Moles of Cl present = 2*0.004346 = 0.008692 moles

Molar mass of Cl =35.5 grams/mole

Weight of chlorine = 0.308566 grams

Now let uf first evaluate mass of SrCl2 ,

Mass of sample with water of hyrdation is 1.7215 grams

Therefore , WSrCl₂.6H₂O+ WCsCl =1.7215 grams

We already know WSrCl₂.6H₂O = 1.15873 grams

Hence, WCsCl = 1.7215-1.15873 = 0.56277 grams

Molar mass of CsCl =168.36 grams/mole

Moles of CsCl = Weight of CsCl /Molar mass of CsCl =0.56277/168.36 = 0.0033426 moles

Weight of Cs in CsCl

1 mole of Cs = 1 mole CsCl =0.0033426 moles

moles of Cs =0.0033426 moles

Molar mass of Cs = 132.9 grams/mole

weight of Cs =moles of Cs * Molar mass of Cs = 0.0033426 *132.9 = 0.44424 grams

weight of Cl in CsCl

1 mole Cl = 1 mole CsCl = 0.0033426 moles

moles of Cl =0.0033426 moles

Molar mass of Cl =35.5 grams/mole

Weight of Cl =0.0033426 *35.5 =0.118623 grams

now for weight percent of Sr, Cs, and Cl in SrCl₂.6H₂O & CsCl sample,

Total weight of original sample = 1.7215 grams

Total weight of Sr = 0.380826 grams

Weight percent of Sr =0.380826/1.7215 *100 =22.122 %

Total weight of Cs = 0.44424

Weight percent of Cs =0.44424/1.7215*100 = 25.8054 %

Total weight of Cl = 0.308566+0.118623 =0.427189 grams

Weight percent of Cl = (0.427189/1.7215)*100 =24.8149 %

The rest 27.2669 % will be of Water

queen_honey_blossom answered 2 years ago

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