2. Calculate the following for the oxygen: (a) The initial mass of copper in the

Question

2. Calculate the following for the oxygen: (a) The initial mass of copper in the moles of copper from the copper sulfate salt (MW of Cu= 63.55 g/mole) (g) (b) The mass of copper oxide obtained (g) (the mass of the copper oxide in the test tube after heating over Bunsen burner to remove water) (c) The gain in mass, equal to the added mass of oxygen (g) Materials Used -50 mL beaker -balance - 5 g Copper sulfate pentahydrate -30 mL of water -test tube Method 2 1. Place empty beaker on balance and record mass: 85.000 g 2.Take empty beaker off balance, place on lab area and then add 5 g of Copper sulfate pentahydrate 3.Place beaker and copper sulfate pentahydrate unto balance and record mass: 90.00 0 g 4·Dissolve copper sulfate pentahydrate by adding 30 mL of water 5.Then add 10 mL of 6M sodium hydroxide Reaction: Color change from blue to transparent 6. Transfer the liquid content to a new beaker and the hard material in the old beaken 7. Place a test tübe on the balance and record mass: 27.400 g place on top of Bunsen bumer ane then allow to cool on workbench before recording n Place on top of Bunsen burmer and then allow to cool on workbench before recording ew mass: 28.993 g

Explanation / Answer

Mass of Cu salt = 90.000 g-85.000 g

= 5.000 g

Now calculate the moles of Cu salt

Amount / molar mass = 5.000 g/ 245.55 g/mol

= 0.0200 mol of Cu salt

Hence one Cu is present in each mole of salt thus 0.00200 mol Cu salt contains 0.00200 mol Cu.

Now calculate the mass of Cu oxide = 28.993 g-27.400 g

= 1.593 g cu oxide

Here 0.0200 Cu is present in this oxide so calculate the mass of Cu and O in this oxide.

Mass of 0.0200 Cu mole = 0.0200 mol*63.55 g/mole

= 1.271 g Cu

Now mass of O in Cu oxide:

Mass of Cu oxide – mass of Cu

= 1.593 g cu oxide- 1.271 g Cu

= 0.322 g O

Now calculate the mole of O as follows:

0.322 g/ 16.00 g/mol=

0.020 mol O

Both are present in 0.020 mol thus the ratio of Cu and O is 1:1.

So empirical formula of Cu oxide is CuO.

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