question on ph and endothermic rcn

[zena]

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hello,

I have 3 q's 😕:

1- if hypochlorous acid is titrated with sodium hydroxide, what is the pH equivalence point --- is it less than 7, greater than 7, 7, or half of pH at half-equivalence point ?

2 - why does sodium chloride readily dissolve in water even though reaction is endothermic --- is it because heat is released when Na and Cl ions are hydrated OR is because heat is required for Na and Cl to be hydrated OR is it because negative entropy change of dissolution results in a net decrease in Gibbs free energy OR is it because the positive entropy change results in net decrease in Gibbs free energy ?

3 - why are many transition elements strongly attracted to magnetic field --- because they form only cations, because most of them are solids at room temperature, because most of them are diamagnetic, because most of them are paramagnetic or is it because most of them have completely filled s orbitals ?

... hoping you can help me

thanks soooo much!!! 🙂

 

[cheesier]

hello,

I have 3 q's 😕:

1- if hypochlorous acid is titrated with sodium hydroxide, what is the pH equivalence point --- is it less than 7, greater than 7, 7, or half of pH at half-equivalence point ?

2 - why does sodium chloride readily dissolve in water even though reaction is endothermic --- is it because heat is released when Na and Cl ions are hydrated OR is because heat is required for Na and Cl to be hydrated OR is it because negative entropy change of dissolution results in a net decrease in Gibbs free energy OR is it because the positive entropy change results in net decrease in Gibbs free energy ?

3 - why are many transition elements strongly attracted to magnetic field --- because they form only cations, because most of them are solids at room temperature, because most of them are diamagnetic, because most of them are paramagnetic or is it because most of them have completely filled s orbitals ?

... hoping you can help me

thanks soooo much!!! 🙂

1) Weak acid + strong base, so it will have a pH over 7.

2) NaCl --> Na + Cl, so there are more molecules present. This means that entropy has increased. G=H-TS, so an increase in S causes a decrease in free energy.

3) If I'm reading the question right, it's because they're paramagnetic.

 

[Isoprop]

Here are some hints and links to help you get to the correct answer.

if hypochlorous acid is titrated with sodium hydroxide, what is the pH equivalence point --- is it less than 7, greater than 7, 7, or half of pH at half-equivalence point ?

At equival. point, what is the major species in solution that determines the pH? By definition, the equival. point is where equal number of moles of NaOH and HClO have reacted to form water and NaClO. The major contributor to NaClO is a base. So what should the pH be?

http://bouman.chem.georgetown.edu/S02/lect19/lect19.htm

why does sodium chloride readily dissolve in water even though reaction is endothermic --- is it because heat is released when Na and Cl ions are hydrated OR is because heat is required for Na and Cl to be hydrated OR is it because negative entropy change of dissolution results in a net decrease in Gibbs free energy OR is it because the positive entropy change results in net decrease in Gibbs free energy ?

This question is really asking why does solvation happen spontaneously. Which of the answer choices explains why something spontaneously?

http://en.wikipedia.org/wiki/Solvation#Thermodynamic_considerations

3 - why are many transition elements strongly attracted to magnetic field --- because they form only cations, because most of them are solids at room temperature, because most of them are diamagnetic, because most of them are paramagnetic or is it because most of them have completely filled s orbitals ?

Are diamagnetic or paramagnetic attracted to a magnetic field? What does it mean to be diagmagnetic? Paramagnetic?

http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/MagneticMatls.htm