You wish to make 25 ml of chromomycin buffer with a final concentration of 0.010 M NaCl, 0.50 mM MgCl2, 0.010 M KCl, and 0.015 mM Na2HPO4. The stock solutions are 0.15 M NaCl, 2.5 M MgCl2, 0.030 M KCl, and 0.010 M Na2HPO4. What amount of each reagent and ddH20 is required to obtain the required 25 ml working solution

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol