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Alla [95]
3 years ago
5

What is the ph of a solution of 0.400 m k2hpo4, potassium hydrogen phosphate?

Chemistry
1 answer:
dusya [7]3 years ago
3 0
When we can get Pka for K2HPO4 =6.86 so we can determine the Ka :

when Pka = - ㏒ Ka

          6.86 = -㏒ Ka 

∴Ka = 1.38 x 10^-7

by using ICE table:

               H2PO4- →  H+  + HPO4
initial      0.4 m            0         0

change     -X                +X       +X

Equ       (0.4-X)               X          X

when Ka = [H+][HPO4] / [H2PO4-]

by substitution:

1.38 X 10^-7 = X^2 / (0.4-X)   by solving for X

∴X = 2.3x 10^-4 

∴[H+] = X = 2.3 x 10^-4

∴PH = -㏒[H+]

        = -㏒ (2.3 x 10^-4)
 ∴PH  =  3.6

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Vitamin c is known chemically by the name ascorbic acid determine the empirical formula of ascorbic acid if it is composed of 40
kow [346]

Answer:

=C_3H_4O_3

Explanation:

When percentage composition is given, and asked for the empirical formula, it is simplest to  assume 100 g of material. Thus,

Mass C = 40.92 g.  Moles C = 40.92 g x 1 mole/12 g = 3.41 moles C

Mass H = 4.58 g.  Moles H = 4.58 g x 1 mole/1.0 g = 4.58 moles H

Mass O = 54.50 g.  Moles O = 54.50 g x 1 mole/16 g = 3.41 moles O

Now, we want to get the moles into whole numbers, so we begin by dividing all by the smallest, i.e. divide all values by 3.41.

Moles C = 3.41/3.41 = 1

Moles H = 4.58/3.41 = 1.34

Moles O = 3.41/3.41 = 1

Now, in order to get 1.34 to be a whole number we multiply it (and all others) by 3

Moles C = 1x3 = 3

Moles H = 1.34x3 = 4

Moles O = 1x3 = 3

Empirical Formula =C_3H_4O_3

3 0
3 years ago
Assuming 100% dissociation, calculate the freezing point and boiling point of 3.11 m K3PO4(aq). Constants may be found here.
aivan3 [116]
Do u have a picture
5 0
3 years ago
Air is compressed from an inlet condition of 100 kPa, 300 K to an exit pressure of 1000 kPa by an internally reversible compress
ElenaW [278]

Answer:

(a) W_{isoentropic}=8.125\frac{kJ}{mol}

(b) W_{polytropic}=7.579\frac{kJ}{mol}

(c) W_{isothermal}=5.743\frac{kJ}{mol}

Explanation:

Hello,

(a) In this case, since entropy remains unchanged, the constant k should be computed for air as an ideal gas by:

\frac{R}{Cp_{air}}=1-\frac{1}{k}  \\\\\frac{8.314}{29.11} =1-\frac{1}{k}\\

0.2856=1-\frac{1}{k}\\\\k=1.4

Next, we compute the final temperature:

T_2=T_1(\frac{p_2}{p_1} )^{1-1/k}=300K(\frac{1000kPa}{100kPa} )^{1-1/1.4}=579.21K

Thus, the work is computed by:

W_{isoentropic}=\frac{kR(T_2-T_1)}{k-1} =\frac{1.4*8.314\frac{J}{mol*K}(579.21K-300K)}{1.4-1}\\\\W_{isoentropic}=8.125\frac{kJ}{mol}

(b) In this case, since n is given, we compute the final temperature as well:

T_2=T_1(\frac{p_2}{p_1} )^{1-1/n}=300K(\frac{1000kPa}{100kPa} )^{1-1/1.3}=510.38K

And the isentropic work:

W_{polytropic}=\frac{nR(T_2-T_1)}{n-1} =\frac{1.3*8.314\frac{J}{mol*K}(510.38-300K)}{1.3-1}\\\\W_{polytropic}=7.579\frac{kJ}{mol}

(c) Finally, for isothermal, final temperature is not required as it could be computed as:

W_{isothermal}=RTln(\frac{p_2}{p_1} )=8.314\frac{J}{mol*K}*300K*ln(\frac{1000kPa}{100kPa} ) \\\\W_{isothermal}=5.743\frac{kJ}{mol}

Regards.

8 0
3 years ago
QUICK QUESTION: On the Bohr model, how come potassium has 19 electrons in its valence shell if potassium has a K+? Isn’t it supp
Vlada [557]

Answer:  K only has 1 valence electron.  It will leave with only a little effort, leaving behind a positively charged K^+1 atom.

Explanation:  A neutral potassium atom has 19 total electrons.  But only 1 of them is in potassium's valence shell.  Valence shell means the outermost s and p orbitals.  Potasium's electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1.  The 4s orbital is the only orbital in the 4th energy level.  So it has a valency of 1.  This means this electron will be the most likely to leave, since it is the lone electron in the oyutermost energy level (4).  When that electron leaves, the charge on the atom go up by 1.  The atom now has a full valence shell of 3s^2 3p^6, the same as argon, Ar.

4 0
3 years ago
Scientists' belief that an atom is a solid sphere, is good enough to explain; PLZ I HAVE LESS TIME!!!!
Natasha2012 [34]

Answer:

Its quite vague, instead you could say an atom is the smallest building block which further consists of subatomic particles like protons, neutrons and electrons :)

Hope thi helps :) and I'd appreciate if you'd mark brainliest because ive been stuck on the same rank for quite a long time :(

7 0
3 years ago
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