NaOH is typically standardized using potassium hydrogen phthalate (KHP).

As an FDA physiologist, you need 0.625 L of phosphoric acid acid / dihydrogen phosphate (H3PO4 (aq) / H2PO4 - (aq) ) buffer with

aksik [14]

Answer:

0.4058L of 1.0M H3PO4

0.2192L of 1.5M NaOH

Explanation:

The pKa of the H3PO4 / H2PO4- buffer is 2.12

To solve this question we must use H-H equation for this system:

pH = pKa + log [H2PO4-] / [H3PO4]

2.75 = 2.12 + log [H2PO4-] / [H3PO4]

0.63 = log [H2PO4-] / [H3PO4]

4.2658 = [H2PO4-] / [H3PO4] (1)

Where [] could be taken as the moles of each reactant

As you have H3PO4 solution, the reaction with NaOH is:

H3PO4 + NaOH → H2PO4- + Na+ + H2O

As you can see, both H3PO4 and H2PO4- comes from the same 1.0M H3PO4 solution

The moles of H3PO4 are:

[H3PO4] = Moles H3PO4 - Moles NaOH

And for H2PO4-:

[H2PO4-] = Moles NaOH added

Replacing in (1):

4.2658 = [Moles NaOH] / [Moles H3PO4 - Moles NaOH]

4.2658 Moles H3PO4 - 4.2658 moles NaOH = Moles NaOH

4.2658 Moles H3PO4 = 5.2658 moles NaOH (1)

In volume:

0.625L = Moles H3PO4 / 1.0M + Moles NaOH / 1.5M

0.625 = Mol H3PO4 + 0.6667 Moles NaOH (2)

Replacing (2) in (1):

4.2658 Moles H3PO4 = 5.2658 (0.625 - Mol H3PO4 / 0.6667)

4.2658 Moles H3PO4 = 5.2658 (0.625 - Mol H3PO4) / 0.6667

4.2658 Moles H3PO4 = 5.2658*(0.9375 - 1.5 mol H3PO4)

4.2658 Moles H3PO4 = 4.9367 -7.8983 mol H3PO4

12.1641 mol H3PO4 = 4.9367

Mol H3PO4 = 0.4058moles * (1L / 1.0moles) =

0.4058L of 1.0M H3PO4

And:

0.625L - 0.4058L =

0.2192L of 1.5M NaOH

5 0

3 years ago

Make a checklist of eight good characteristics of a experiment.

natka813 [3]

I could only find 7!

- independent variable
- dependent variable
- control group
- experimental group
- constant
- observation
- inference

6 0

4 years ago

In this photograph what rock formation is presented by the blue lines?

Effectus [21]

It is representing syncline rock formation

there are two rock formation based on fold formation : syncline and anticline

In syncline rock formation there is fold like trough unlike anticline where it is like crust

In syncline the fold is downward as shown in photo and the new rock is outer fold and old at inner side

3 0

4 years ago

Read 2 more answers

A 9.75 L 9.75 L container holds a mixture of two gases at 41 ° C. 41 °C. The partial pressures of gas A and gas B, respectively,

Triss [41]

Answer:

The total pressure P = 1.642 atm

Explanation:

From the dalton's law

Total pressure of the mixture is

$P = P_{A} + P_{B} + P_{C}$ ----- (1)

$P_A = 0.419$ atm

$P_B = 0.589$ atm

$P_C = \frac{nRT}{V}$

n = 0.24 mole

R = $0.0821$ $\frac{L.Atm}{K.mol}$

T = 41 °c = 314 K

$P_C = \frac{(0.24)(0.0821)(314)}{9.75}$

$P_C$ = 0.634 atm

From equation (1)

P = 0.419 + 0.589 + 0.634

P = 1.642 atm

Thus the total pressure P = 1.642 atm

3 0

3 years ago

Which statement describes sunspots? A.Sunspots have a bright white appearance. B.Sunspots occur in the radiative zone of the sun

Ugo [173]

Answer:

The statements that describe sunspots is;

D. Sunspots have lower temperatures than their surroundings

Explanation:

Sunspots is a phenomenon that involves temporary appearance of dark areas on the Sun's surface, which are regions of concentrated magnetic field flux which inhibit heat transfer by convection and are therefore cooler than other parts of the Sun. Due to the presence of magnetic field magnetic

Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Opposite magnetic polarity sunspots usually appear as a pair.

Therefore, the statement that best describe sunspots is that a sunspot is a region of reduced temperature compared to surrounding areas on the Sun's surface.

8 0

3 years ago