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3 years ago

A solution has a pH of 2.5. What is its [OH-] ?

Chemistry

1 answer:

SVETLANKA909090 [29]3 years ago

6 0

pH + pOH = 14

pH = 2.5 then pOH = 11.5

[OH-] = 10^(-pOH) =10^(-11.5)

= 3.2 x 10^(-12)

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Convert the composition of the following alloy from atom percent to weight percent (a) 44.9 at% of silver, (b) 46.3 at% of gold,

vesna_86 [32]

Answer:

Mass percentage of gold : 33.35%

Mass percentage of silver: 62.80%

Mass percentage of copper : 3.85%

Explanation:

$N=n\times N_A$

Where : N = Number of atoms

n = moles

$N_A=6.022\times 10^{23}$ = Avogadro number

Let the total atoms present in the alloy be 100.

Atom percentage of silver = 44.9%

Atoms of of silver = 44.9% of 100 atoms = 44.9

Atomic weight of silver = 107.87 g/mol

Mass of 44.9 silver atoms = 107.87 g/mol × 44.9 = 4,843.363 g/mol

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Mass of 44.9 gold atoms = 196.97 g/mol × 46.3 = 9,119.711 g/mol

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Atoms of of copper = 8.8% of 100 atoms = 8.8

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Total mass of an alloy :4,843.363 g/mol + 9,119.711 g/mol + 559.24 g/mol

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$\frac{4,843.363 g/mol}{4,843.363 g/mol + 9,119.711 g/mol + 559.24 g/mol}\times 100=33.35 \%$

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$\frac{9,119.711 g/mol}{4,843.363 g/mol + 9,119.711 g/mol + 559.24 g/mol}\times 100=62.80\%$

Mass percentage of copper :

$\frac{559.24 g/mol}{4,843.363 g/mol + 9,119.711 g/mol + 559.24 g/mol}\times 100=3.85\%$

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