username4386034
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Hi! I need help on this A Level Developing Metals homework questions:1.0g of brass was dissolved into 50cm3 of nitric(V) acid to form a blue aqueous solution.The solution was found to have a concentration of 0.19mol/dm3.1) State the formula of the ionic substance in the blue solution [1]2) Name the other product of the reaction [1]3) State the formula of the complex ion in solution [1]4) Explain why the solution is blue [4]5) Calculate the % of copper in brass. Give the appropriate number of sig. fig. [3]6) Describe 2 practical procedures that could be used to obtain the concentration of the solution. [4]7) Explain, in terms of electron configurations, why all of the blue colour in the solution can be attributed to the copper ions [3]A small volume of ammonia solution was added to the blue copper solution followed by an excess.8) Describe and explain what would be observed in these 2 steps.Use equations to show these changes. [6]
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charco
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(Original post by eilloh)
Hi! I need help on this A Level Developing Metals homework questions:1.0g of brass was dissolved into 50cm3 of nitric(V) acid to form a blue aqueous solution.The solution was found to have a concentration of 0.19mol/dm3.1) State the formula of the ionic substance in the blue solution [1]2) Name the other product of the reaction [1]3) State the formula of the complex ion in solution [1]4) Explain why the solution is blue [4]5) Calculate the % of copper in brass. Give the appropriate number of sig. fig. [3]6) Describe 2 practical procedures that could be used to obtain the concentration of the solution. [4]7) Explain, in terms of electron configurations, why all of the blue colour in the solution can be attributed to the copper ions [3]A small volume of ammonia solution was added to the blue copper solution followed by an excess.8) Describe and explain what would be observed in these 2 steps.Use equations to show these changes. [6]
Which part do you need "help" with? There are 8 questions here ...
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username4386034
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Mr.noname
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1. Brass is an alloy of copper and zinc. By considering both metals decide which is likely to form a coloured compound (only transition metals form coloured compounds) and what compound will that be based on the acid it reacts with.
2.) Other product can be worked out based on 1.)
3.) Transition metals form a hexaaqua complex with water ligands
4.) You can explain the color based on splitting of d orbitals and electron/d-d transitions etc. (mention something about the compliment colour)
5.) use conc. and volume given to calculate moles of copper and attempt to find the % by mass of copper in brass.
6.) it's a coloured compound think about how you can find the concentration of coloured compounds.
7.) Compare the EC of copper and zinc , you know that zinc only has one stable ion Zn2+ So explain why only copper can be a coloured ion while zinc cannot. ( once again ,have to talk about electron/d-d transitions.)
8.) This part is to do with acid-base reaction and ligand substitution. You need to have knowledge on copper as a transition metal for the equations. For observations you need to mention what you see as ammonia is added dropwise to excess, two characteristics things occur during the course of the reaction depending on how much ammonia is added.

TSR isn't a homework service you should at least show what you have done and people can help you based on that.
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