3. Use the mole ratio of CuO produced per mole of malachite to write a balanced equation for the malachite decomposition reaction. Assume that CO₂ is also a product of the decomposition.
CuCo3*Cu9OH)2 -----> 2Cuo+Co2+H2O
0.004522431 moles of malachite
0.01257071 moles of CuO
4. Predict the mass of CuO expected to result from the decomposition of the malachite, based on the balanced equation. 1g of Malachite was given. The mass of CuO produced (g): 0.72g
5. Compare the mass obtained from the mass predicted, and discuss reasons for any discrepancy.
3 answers
It appears t me that 0.00452 moles malachite should have produced 2x that for CuO. Is that 0.0126 mols your experimental value? If so it is too high. I have no idea what may have gone wrong. You have provided no details for the experiment.
(a) Mass of an empty Erlenmeyer flask (g): 91.780g
(b) Mass of the Erlenmeyer flask with malachite(g): 92.780g
(c) Subtract (a) from (b) to obtain the mass of malachite (g): 1g
(c) Mass of Erlenmeyer flask with CuO(g): 92.500g
(d) Subtract (a) from (c) to obtain the mass of CuO produced (g): 0.72g
2. Calculate the following:
(a) moles of malachite in 1g: 222.1mw
0.004522431 moles of malachite
(b) moles of CuO produced: 79.55 mw
0.01257071 moles of CuO
(b) Mass of the Erlenmeyer flask with malachite(g): 92.780g
(c) Subtract (a) from (b) to obtain the mass of malachite (g): 1g
(c) Mass of Erlenmeyer flask with CuO(g): 92.500g
(d) Subtract (a) from (c) to obtain the mass of CuO produced (g): 0.72g
2. Calculate the following:
(a) moles of malachite in 1g: 222.1mw
0.004522431 moles of malachite
(b) moles of CuO produced: 79.55 mw
0.01257071 moles of CuO
If I read this right,
moles malachite in 1 g i 1/221.12 = 0.0452 (we have a slight difference in molar mass malachite--based on CuCO3.Cu(OH)2 I found 221.12) but that changes your value insignificantly.
Next. 0.72 looks ok BUT moles from that does not. If I divide 0.72/79.55 I get 0.00905 and not the 0.0126 you have.
Based on the 0.00452 moles of malachite you took you should have obtained 0.00452 x 2 = 0.00904 and that is just about as good as it gets in lab work.You don't have an error to explain. :-).
moles malachite in 1 g i 1/221.12 = 0.0452 (we have a slight difference in molar mass malachite--based on CuCO3.Cu(OH)2 I found 221.12) but that changes your value insignificantly.
Next. 0.72 looks ok BUT moles from that does not. If I divide 0.72/79.55 I get 0.00905 and not the 0.0126 you have.
Based on the 0.00452 moles of malachite you took you should have obtained 0.00452 x 2 = 0.00904 and that is just about as good as it gets in lab work.You don't have an error to explain. :-).
1 answer