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3 years ago

Calculate the concentration of all species in a 0.165 m solution of h2co3.

Chemistry

1 answer:

xxMikexx [17]3 years ago

3 0

(1) H2CO3 + H2O --> HCO3- + H3O+ [Ka = 4.5E-7]

(2) HCO3- + H2O --> CO32- + H3O+ [Ka = 4.7E-11]

Observe that the two Ka values differ from each other drastically. This will mean that in terms of pH, ONLY THE FIRST IONIZATION WILL AFFECT pH.

(1) H2CO3 + H2O --> HCO3- + H3O+ [Ka = 4.5E-7]

I.....0.165M..................0..........

C......-x......................+x........

E....0.165-x.................x...........

4.5E-7 = x^2/(0.165-x) <-- use the appoximation rule because Ka is very small

2.72E-4 = x

Thus, from equation (1), we see that the [H3O+] = 2.72E-4M, [H2CO3] = 0.165M, and [HCO3-]= 2.72E-4M. Note that THIS step will determine the pH of the polyprotic acid

To calculate the last species, just transfer these values the next equation

(2) HCO3- + H2O --> CO32- + H3O+ [Ka = 4.7E-11]

I....2.72E-4..................0..........

4.7E-11 = (x*2.72E-4)/2.72E-4

4.7E-11 = x = [CO32-]

To calculate the OH- from H3O+, just find the pH of H3O+, subtract it from 14 to find the pOH, and find the [OH-] from that.

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Write the atomic symbol for the isotope of bismuth with 125 neutrons.

vlada-n [284]

First, isotopes are the atoms of a single element whose nuclei have a different number of neutrons, and therefore, differ in mass numbers. You should know that atoms are formed by a nucleus that has a small size and is made up of protons and neutrons. The nucleus is surrounded by a cloud of electrons, which are found in a region of the atom called the cortex.

The mass number, represented as A, is the sum of the number of protons and neutrons in the nucleus. On the other hand, the atomic number (Z) is the number of protons that exist in the nucleus.

The isotopes of an element X are represented as follows,

(see first attached picture)

It should be noted that the number of neutrons of a chemical element can be calculated as the difference A-Z.

The atomic and mass numbers of bismuth with 125 neutrons are:

Z = 83

A = 83 + 125 = 208

Thus, the atomic symbol of the bismuth isotope with 125 neutrons is:

(see second attached picture)