you have to prepare a ph 5.03 buffer, and you have the following 0.10m solutions available: hcooh, hcoona, ch3cooh, ch3coona, hcn, and nacn. How many milliliters of each solution would you use to make approximately a liter of the buffer?

Solution :

The buffer is the one that contains weak acid (the is nearly equal to the required pH) and the salt of its conjugate base.

The  values of the given weak acids are as follows :

HCOOH :  = 3.744

HCN : = 9.21

Since the required pH is 5.03, the suitable buffer is the mixture of the acetic acid and the salt of its conjugate base.

Let suppose the volumes of and are x and y mL respectively.

So the total volume of the buffer is 1000 mL.

∴   x+ y = 1000  ................(1)

Writing the Henderson-Hasselbalch equation for the given buffer solution :

  .............(2)

y = 1.9 x

Substituting the values of y in equation (1), we get

x + 1.9 x = 1000

x = 345

Putting the value of x in (1), we get

345 + y = 1000

y = 655

Therefore the volume of is 345 mL and the volume of is 655 mL.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.