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zhenek [66]
4 years ago
15

1.

Chemistry
1 answer:
zysi [14]4 years ago
5 0
A. No need technique
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How many liters of 0.615 M NaOH will be needed to raise the pH of 0.385 L of 5.13 M sulfurous acid (H2SO3) to a pH of 6.247?
givi [52]

Answer:

Volume of NaOH required = 3.61 L

Explanation:

H2SO3 is a diprotic acid i.e. it will have two dissociation constants given as follows:

H2SO3\leftrightarrow H^{+}+HSO3^{-} --------(1)

where,  Ka1 = 1.5 x 10–2  or pKa1 = 1.824

HSO3^{-}\leftrightarrow H^{+}+SO3^{2-} --------(2)

where,  Ka2 = 1.0 x 10–7 or pKa2 = 7.000

The required pH = 6.247 which is beyond the first equivalence point but within the second equivalence point.

Step 1:

Based on equation(1), at the first eq point:

moles of H2SO3 = moles of NaOH

i.e. \ 5.13\  moles/L*0.385L = moles\  NaOH\\therefore, \ moles\  NaOH = 1.98\ moles\\V(NaOH)\ required = \frac{1.98\ moles}{0.615\ moles/L} =3.22L

Step 2:

For the second equivalence point setup an ICE table:

                  HSO3^{-}+OH^{-}\leftrightarrow H2O+SO3^{2-}

Initial           1.98                    ?                                       0

Change      -x                       -x                                       x

Equil           1.98-x                 ?-x                                    x

Here, ?-x =0 i.e. amount of OH- = x

Based on the Henderson buffer equation:

pH = pKa2 + log\frac{[SO3]^{2-} }{[HSO3]^{-} } \\6.247 = 7.00 + log\frac{x}{(1.98-x)} \\x=0.634 moles

Volume of NaOH required is:

\frac{0.634\ moles}{0.615 moles/L}=0.389L

Step 3:

Total volume of NaOH required = 3.22+0.389 =3.61 L

3 0
3 years ago
Which of the following represents an element?<br>со<br>H2CO3<br>02<br>ОН-​
LenKa [72]

Answer:

Co (assuming there's a typo in not capitalizing the first letter)

Explanation:

The elements are depicted in the periodic table. Those are fundamental atoms that are not bonded to anything else but exist in their natural states without forming a bond with anything. That said, we're interested in a monoatomic species listed (the species which consist from only one single atom).

Out of all the choices, we have Co, cobalt, which is a single atom and can be found as an element with the atomic number 27.

Carbonic acid, H_2CO_3, consists of 3 different elements: hydrogen (atomic number of 1), carbon (atomic number of 6) and oxygen (atomic number of 8). It's a compound rather than an element, as it consists of several atoms bonded together.

Oxygen, O_2, is also a molecule. It consists of more than a single atom, even though the two atoms are identical. We have a compound, oxygen gas, which consists of two same oxygen (O) atoms (or elements).

Hydroxide anion, OH^{-}, also consists of two elements: oxygen and hydrogen. It also contains a charge on it, so rather than being a molecule, this is now an ion. Since it consists of more than a single atom, this is not an element as well.

6 0
4 years ago
Which of the following statements about fats is FALSE?
Assoli18 [71]

Answer:

They dissolve easily in the body’s fluids

8 0
3 years ago
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rusak2 [61]
The answer to your question is c , Natural selection
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When water changes state in the water cycle, the total number of water particles remains the same. The changes of state include melting, sublimation, evaporation, freezing, condensation, and deposition. All changes of state involve the transfer of energy.
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