Epsom salt is MgS0_4 7 H_20. What does the chemical formula become when this hyd

Question

Epsom salt is MgS0_4 7 H_20. What does the chemical formula become when this hydrate is gently heated? A 1000 g sample of an unknown hydrate of cobalt chloride is gently dehydrated. The resulting mass is 0.546 g. The cobalt is isolated and weighs 0 248 g. What is the empirical (experimentally determined) formula of the hydrate? Report each answer to the proper number of significant figures. Show your work. Determine the number of moles of water lost from the hydrated unknown. _ 1.000 g - 0, 546 g = Determine the number of moles of cobalt collected. _ 0.248 g of cobalt Determine the number of moles of chloride in the compound. _ 0.56 g - 0.248 g

Explanation / Answer

2) Epsom salt when heated gently will start to lose its water molecules and at first it will go to monhydrated(1H2O) state from heptahydrated(7H2O) and then it will become anhydrous magnesium sulphate (MgSO4) with water molecule

3) Given:    Intial mass of hydrate of Cobalt Chloride = 1.000 g

Mass of dehydrated Cobalt Chloride (CoCl2)= 0.546 g

Mass of hydrade in hydrate of Cobalt chloride = 1.000 g - 0.546 g = 0.454 g

Mass of isolated Cobalt (Co)   = 0.248 g

Mass of Chloride in Cobalt Chloride = 0.546 g - 0.248 g = 0.298 g

Molecular weight of (CoCl2) = 129.84 g/mol

Molecular weight of (Co) = 58.94 g/mol

Molecular weight of (Cl) = 35.5 g/mol

Molecular weight of (H2O) = 18 g/mol

(b) Number of moles of Water lost from hydrate = mass of water lost from hydrate / Mol. Wt. of H2O

                                                                            = 0.454 g / 18 g/mol   =25.22 * 10-3 Moles

Number of moles of Water lost from hydrate = 25.22 * 10-3 Moles                                      Answer 3(a)

(b) Number of moles of Cobalt collected = mass of Co/ Mol. Wt. of Co = 0.248 g / 58.94 g/mol =4.21 * 10-3 Moles

Number of moles of Cobalt collected = 4.21 * 10-3 Moles                                      Answer 3(b)

(c) Number of moles of Chloride = mass of Cl/ Mol. Wt. of Cl = 0.298 g / 35.5 g/mol = 8.394 * 10-3 Moles

Number of moles of Chloride = 8.394 * 10-3 Moles                                 Answer 3(c)

No of moles of Cobalt = no of moles of CoCl2 = No. of moles of Cl2 /2     = 4.21 * 10-3 Moles

No of hydrate in hydrate of CoCl2 = No of moles of water / No. of moles of CoCl2 = 25.22* 10-3 / 4.21 * 10-3

No of hydrate in hydrate of CoCl2 = 6

So formula for hydrate of cobalt chloride = CoCl2.6H2O

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