Three Chemistry Calculation Problems (Preliminary) (1 Viewer)

[locked.on]

Three questions that I've been having problems with:

1. One method of extracting nickel from concentrated ores is to mix finely divided ore with carbon monoxide. Nickel reacts to form gaseous nickel carbonyl. When excess nickel was reacted with 500mL CO, 125mL nickel carbonyl was formed at the same temperature and pressure. Assuming all the CO reacted, what is the formula of nickel carbonyl? Explain how you deduced this.
   
   
2. A silver coin was analysed and found to contain only silver and copper. 1.580g of this coin was dissolved in concentrated nitric acid and the resultant solution diluted. Reaction of the solution with excess hydrochloric acid yielded 1.050g of silver chloride. Calculate the percentage of silver in the sample.
   
   
3. A sample of iron wire reacts with oxygen to form iron (III) oxide. If 3.58g of the wire yields 5.00g of the iron (III) oxide, calculate the percentage purity of the iron.

Any help, hints or solutions would be much appreciated!

 

[minijumbuk]

1. I don't know what the other product is, nor do I know what the ore is. I'm assuming that either the question is wrong, or I am incapable of answering it.

2. 2Ag(s) + 2HNO3(aq) --> 2AgNO3(aq) + H2(g)
AgNO3(aq) + HCl(aq) --> AgCl(s) + HNO3(aq)

Cu is a weaker reducing agent than H+, so will not react


Moles of AgCl = 1.05 g / (107.9 +35.45) g/mol
= X mol (press this on the calculator yourself xD)

Therefore X mol AgNO3 reacted (molar ratio 1:1)
And hence, X mol Ag reacted in first equation to form X mol AgNO3 (molar ratio of Ag : AgNO3 = 2:2 = 1:1)

Hence, Mass of Ag = X mol x 107.9

Therefore mass percentage of Silver in the coin mixture = (107.9 x X) / 1.58 x 100%

3. 4Fe(s) + 3O2(g) --> 2Fe2O3 (s)

Moles of Fe2O3 = 5g/(2x55.85 + 3x16)g/mol
= X mol
Therefore 2X mol Fe reacted

Mass of 2X mol of Fe = 2X x 55.85
= Y grams

Therefore percentage purity of iron in the wire = Y/3.58 x 100 %

 

[vds700]

1. The way I would approach it is:

xNi + yCO ->Ni[FONT=&quot]_x(CO)[/FONT][FONT=&quot]_y

moles of CO = mass/mw = 500/28 = 17.86

therefoore y = 17.86

moles of Ni[/FONT][FONT=&quot]_x(CO)[/FONT][FONT=&quot]_y = 125/(x * 58.69 +28 * 17.86)
= 125/(58.69x + 500.08)

molar ratio is x : 17.86 : 125/(58.69x + 500.08)

somehow u have to solve for x, im not sure exactly how. Maybe someone else can help. Once u know x, u can simplify things down and hopefuly work out the formula.
[/FONT]

 

[minijumbuk]

But the Nickel was in the form of ores =\

 

[vds700]

But the Nickel was in the form of ores =\

yes but the actual question said that "excess" nickel reacted with CO to form nickel carbonyl, so i assumed that to mean nickel on its own, not in an ore (they dont tell you what the ore is anyway).

 

[minijumbuk]

But that just screws the whole purpose of "extraction" =\

What I think is that the question is flawed.

 

[Undermyskin]

Er... what do you mean? That's the whole point of extracting Ni from its ore.: letting Ni react with CO.