Anonymous32

I am very sorry that I did not give a full explanation. 

1(a) (i) Oxidation state of indium: 

3+ as indium is in group 3

ii)Equation for indium metal and dilute nitric acid: 

In(s) + 3HNO3 (aq) In(NO3)3 (aq) + 3/2H2 (g)

(iii) Oxidised species: Reduced species:

Oxidised: Indium

Reduced: Hydrogen

(iv) Equation for indium metal and conc. nitric acid:

In(s) + 4HNO3 (aq) In(NO3)3 (aq) + NO + 2H2O(l)

 (v) Equation for formation of indium hydroxide:

(vi) Equation for formation of indium oxide:

(vii) Maximum mass of indium oxide:

I have stated the whole question along with the answers for each part. From part v onwards, I am stuck. I believe this is a step-by-step process where we have to use the products from the previous reaction to solve the next part. However, I am confused how they expect us to write an equation using one compound. This question is from the Cambridge Chemistry Challenge. I am very sorry that I did not fully explain this question, but I hope this helps and any help would be highly appreciated. Thank you!

the formation of indium nitrate using indium metal and concentrated nitric acid 

how do you form indium hydroxide using indium nitrate? 

the equation for fromation of indium nitrate is In +4HNO3 --> 2In(NO3)3 + NO +3H20 

2 hours ago, Phi for All said:

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Moderator Note

Can you do us a favor and put Homework Help questions in Homework Help? Science Education is for news about teaching science.

 

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Moderator Note

Also, it would help if you expand just a bit on your titles. All of them look the same, which makes it difficult for others to remember which they've replied to. 

 

sorry, i will make sure to do that next time!

1 hour ago, exchemist said:

Depends what you are trying to do. If you just want to show what is bonded to what then it doesn’t matter, but if you want show spatial relationships then bond angles can become important. 

yes, i wanted to show what is bonded to what, thank you!

when you draw the displayed formula of a molecule, does it matter how you draw it as long as each atom makes the right number of bonds?
for example, does it matter what the molecule C3H4O3 looks like as long as the carbon makes 4 bonds each, the oxygen 2 and the hydrogen 1?

48 minutes ago, exchemist said:

Look, we are very willing to help, but you have to show you are making some effort for yourself, first. We want to help you learn, not to do the work for you so that you learn nothing. What you have written isn't even a sentence. 

don't worry, i have figured it out thanks

The half equation for the conversion of hydrazine to nitrogen gas.

how do i balance this half equation
NO2- + H+--> NH2OH +H20

sorry nvm i worked it out

thank you!

5 minutes ago, Sensei said:

This is a clever question in physics.

Do you know the equation of the distance traveled by an object falling at a given acceleration? Reverse it to have time as result and distance and acceleration as parameters.

The distance is known. The acceleration is known. Only the time is unknown.

Have two such equations, but with different accelerations of 10 m/s^2 and 9.8 m/s^2, and divide them together and multiply by 100% to get the percentage difference, and subtract to have the absolute time difference in seconds.

thank you so much, i was so stuck on it, this was very helpful!!

i also have two questions

1) when recording a force value, should it be to 2 significant figures

2)A car starts from rest and accelerates down a slope. The acceleration remains constant as the car travels from the top to the bottom of the slope. The average speed of the car is 2 m/s. The speed of the car as it reaches the bottom of the slope is: A. 0 m/s B. Between 0 m/s and 2 m/s C. 2 m/s D. Between 2 m/s and 4 m/s E. 4 m/s F. Greater than 4 m/s

acceleration= change in velocity/time taken?

A student predicts that a steel ball dropped from rest from a height of 2 m will hit the floor
after 0.63 seconds. In their calculation they used an approximate value for the acceleration
due to gravity of g = 10 m/s2
.
The accepted value for the acceleration due to gravity is g = 9.8 m/s2
.
This means their calculated time will be:
A. unaffected
B. too long by about 1%
C. too short by about 1%
D. too long by about 0.2 seconds
E. too short by about 0.2 seconds

A car starts from rest and accelerates down a slope. The acceleration remains constant as the car travels from the top to the bottom of the slope. The average speed of the car is 2 m/s. The speed of the car as it reaches the bottom of the slope is: A. 0 m/s B. Between 0 m/s and 2 m/s C. 2 m/s D. Between 2 m/s and 4 m/s E. 4 m/s F. Greater than 4 m/s

does anyone know any hard biology questions i can do applying gcse knowledge but not gcse style questions?

Hi,

Does anyone have the answers to the 20201 past paper for the biology Olympiad? I am currently preparing for it and there is no mark scheme and the answers aren't online. Any help will be very much appreciated! Thank you!!!

thank you, i understand my mistake now!

for part ii, i did 0.519/7400 which gives a concentration of 7.0135*10-5 mol/dm3

b) Breakfast cereals frequently have elemental iron added to them as a dietary supplement. A method for making a quantitative measurement of the amount of iron is to use the reaction between Fe3+(aq) and thiocyanate, SCN– (aq), which gives the deep red complex FeSCN2+(aq). Fe3+(aq) ൅ SCN– (aq) ื FeSCN2+(aq) The depth of the colour can be measured using a spectrophotometer which gives a value for the absorbance that is proportional to the concentration of the complex: absorbance ൌ constant ൈ [FeSCN2+] Equation 1 The constant can be found by measuring the absorbance of a solution of known concentration.

(i) The absorbance of a solution of the complex with concentration 2.5 ൈ 10–4 moldm–3 was measured to be 1.85; determine the value of the constant in Equation 1.

100 g of breakfast cereal was mixed with sufficient dilute acid to dissolve all of the iron. The solution was carefully filtered and mixed with sufficient oxidising agent to convert all of the iron to Fe3+. The solution was made up to a total volume of 250cm3 . 10.0cm3 of this solution was mixed with 10.0cm3 of a solution of thiocyanate; you may assume that all of the iron is converted to the complex. The absorbance of the resulting solution was measured as 0.519.

(ii) Using the value of the constant found in (i), calculate the concentration of Fe3+ in the solution for which the absorbance was measured. [2 marks]

(iii) Hence calculate the concentration of Fe3+ in the solution prepared from the cereal.

I have done part 1 and part 2 however for part 3 shouldn't the concentration of fe3+ in the solution be 25 greater than the concentration calculated in part 2 since the volume of solution is 25 times greater?

please can i have help on part iii of this question. thanks!

nsaa question 2.docx