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# Calculation on chem watch

1. Hi, can someone help me on question 1 part b (vi) and part d(i). Please and thank you Attachment 694502694504
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2. (Original post by Snowie9)
Hi, can someone help me on question 1 part b (vi) and part d(i). Please and thank you Attachment 694502694504
Here's the answer for the first few questions before question 1 part (vi). I just couldn't understand how to get the answer for that and for the balancing equation, can someone teach me how. I tried balancing the oxidation number but still couldn't get it
3. The answer for b part iv) is derived from the part iii), in part iii) we found out that the moles of MnO4- used in the reaction was 3 x 10^-4 mol.

Since 5 moles of Fe2+ reacts with 1 mole of MnO4-, the moles of Fe2+ actually used was 5 x (3 x 10^-4)
4. (Original post by Metanoia)
The answer for b part iv) is derived from the part iii), in part iii) we found out that the moles of MnO4- used in the reaction was 3 x 10^-4 mol.

Since 5 moles of Fe2+ reacts with 1 mole of MnO4-, the moles of Fe2+ actually used was 5 x (3 x 10^-4)
No, i'm asking for question b last part, calculate the mass of copper that could be dissolved
5. (Original post by Snowie9)
No, i'm asking for question b last part, calculate the mass of copper that could be dissolved

From part v) we have figured out that of the 1.5M of Fe3+, 0.6 M has been converted in Fe2+.

This means that the concentration of Fe3+ in the remaining mixture is 0.9M

To know the amount of copper that can react with this 100 cm^3 of this mixture.
a) moles of Fe3+ in 100 cm^3 = 0.9 x 0.1 = 0.09 moles
b) moles of copper that will react (based on the first equation) = 0.09/2 = 0.045
c) mass of copper = 0.045 x Ar of copper
6. (Original post by Metanoia)

From part v) we have figured out that of the 1.5M of Fe3+, 0.6 M has been converted in Fe2+.

This means that the concentration of Fe3+ in the remaining mixture is 0.9M

To know the amount of copper that can react with this 100 cm^3 of this mixture.
a) moles of Fe3+ in 100 cm^3 = 0.9 x 0.1 = 0.09 moles
b) moles of copper that will react (based on the first equation) = 0.09/2 = 0.045
c) mass of copper = 0.045 x Ar of copper
I see! Thanks so much! Would you mind helping me on part d(i)? I couldn't balance the equation
7. (Original post by Snowie9)
I see! Thanks so much! Would you mind helping me on part d(i)? I couldn't balance the equation
I assumed that you had no difficulty figuring out the respective oxidation numbers of Si and H before and after the reaction.

The tricky part was to determine the ratio of moles of SiO2 formed with H2.

The total increase in oxidation numbers must be equal to the total decrease in oxidation numbers.

Therefore SiO2 : H2 is 1:4
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8. (Original post by Metanoia)
I assumed that you had no difficulty figuring out the respective oxidation numbers of Si and H before and after the reaction.

The tricky part was to determine the ratio of moles of SiO2 formed with H2.

The total increase in oxidation numbers must be equal to the total decrease in oxidation numbers.

Therefore SiO2 : H2 is 1:4
Thank you so much!!

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