Phosphoric acid is a triprotic acid with the following pka values:

pka1=2.148, pka2=7.198, pka3=12.375

you wish to prepare 1.000 l of a 0.0500 m phosphate buffer at ph 7.540. to do this, you choose to mix the two salt forms involved in the second ionization, nah2po4 and na2hpo4, in a 1.000 l volumetric flask and add water to the mark. what mass of each salt will you add to the mixture?

mass nah2po4

mass na2hpo4

what other combination of phosphoric acid and/or its salts could be mixed to prepare this buffer? (check all that apply).

h3po4 and nah2po4

h3po4 and na2hpo4

h3po4 and na3hpo4

nah2po4 and na3po4

na2hpo4 and na3po4

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :

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geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.

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