In the following reaction the iodide ion (i-) in hi is oxidized by the permanganate ion ( a 5.0 ml solution of 0.20m hi requires 4.0 ml of kmno4 to completely oxidize all the iodide. what is the molarity of the kmno4 solution?
10 hi + 2 kmno4 + 3 h2so4 → 5 i2 + 2 mnso4 + 8 h2o
1)0.05 m
2)0.16 m
3)0.25 m
4)0.8 m

The molarity of the KMnO4 solution is 0.05M (option 1)

Explanation:

10 HI + 2 KMnO4 + 3 H2SO4 → 5 I2 + 2 MnSO4 + 8 H2O

This is the base.

10 moles of HI need 2 moles of KMnO4, to make 5 moles of I2 (gas)

Our solution of HI is 0,20 M which means 0,2 moles in 1 L of solution but we used 5 mL, so how many moles did we use?

Molarity . volume = Moles

0.2 moles/L  . 0.005L = 0.001 moles

Notice, we had to convert 5 mL into 0.005 L

So, let's go back to begining: 10 moles of HI need 2 moles of KMnO4.

How many moles of salt, do we need for 0.001 moles of HI.

The rule of three is:

10 moles of HI ___ need ___ 2 moles of KMnO4

0.001 moles of HI __ need ___ (0.001 . 2 ) / 10 = 0.0002 moles

This is our quantity of moles, that we need from KMnO4 but this moles are in 4 mL.

Molarity = moles / L but we can also take account molarity as mM / mL (Molarity/1000)

0.0002 moles . 1000 = 0.2 mM

0.2 mM / 4mL = 0.05 M

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.