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3 years ago

What is the pH of a mixture of 0.042 M NaH2PO4 and 0.058 M Na2HPO4? Hint: The pKa of phosphate is 6.86.

Chemistry

1 answer:

AlekseyPX3 years ago

5 0

Answer:

The pH value of the mixture will be 7.00

Explanation:

Mono and disodium hydrogen phosphate mixture act as a buffer to maintain pH value around 7. Henderson–Hasselbalch equation is used to determine the pH value of a buffer mixture, which is mathematically expressed as,

$pH=pK_{a} + log(\frac{[Base]}{[Acid]})$

According to the given conditions, the equation will become as follow

$pH=pK_{a} + log(\frac{[Na_{2}HPO_{4} ]}{[NaH_{2}PO_{4}]})$

The base and acid are assigned by observing the pKa values of both the compounds; smaller value means more acidic. NaH₂PO₄ has a pKa value of 6.86, while Na₂HPO₄ has a pKa value of 12.32 (not given, but it's a constant). Another more easy way is to the count the acidic hydrogen in the molecular formula; the compound with more acidic hydrogens will be assigned acidic and vice versa.

Placing all the given data we obtain,

$pH=6.86 + log(\frac{0.058}{0.042})$

$pH=7.00$

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Answer:

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3 years ago

Phosphorus atomic radius is smaller than magnesium atomic radius <br> True or false

stealth61 [152]

Answer:

True

Explanation:

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<em>Hence, the atomic radius of phosphorus is smaller than the atomic radius of magnesium. Basically, the atomic radius of phosphorus is 98 pm while the atomic radius of magnesium is 145 pm.</em>

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3 years ago

How many bananas are equal to 7.50 moles of bananas?

Veseljchak [2.6K]

Answer:

4.52×10^24

Explanation:

N = n × Na

where; N = no. of bananas

n = no. of moles

Na = Avogadro's constant

Which is 6.02×10^23

N = 7.5 × 6.02×10^23

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3 years ago

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<h3>Further explanation</h3>

Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d, and f. The maximum number of electrons for each sub-shell is

• s: 2 electrons

• p: 6 electrons

• d: 10 electrons and

• f: 14 electrons

Charging electrons in the sub-shell uses the following sequence:

The element is Oxgen, with symbol O, and :

the atomic number=8=number of electron

the atomic mass=16

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$\tt _8^{16}O:1s^22s^22p^4$ or we can write with noble gas [He] 2s²2p⁴

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3 years ago