Chemistry, 10.10.2019 05:30 Ididntwanttomakethis

Asample of lake water at 25°c is analyzed and the following parameters are found: total alkalinity = 6.2 x 10-4 m phenolphthalein alkalinity = 1.0 x 10pm ph = 7.6 hardness = 30.0 mg/l [mg²+] = 1.0 x 10-4 m extract all possible single-ion concentrations that you can by combining one or more of these data. also determine whether or not the water is at equi- librium with respect to the carbonate-bicarbonate system and whether or not it is saturated with calcium carbonate.

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Answer from: kiridis03

Explanation:

The given data is as follows.

Temperature = $25^{o}C$ , Total alkalinity = $6.2 \times 10^{-4}$ M

Alkalinity of phenolphthalein = $1 \times 10^{-5}$ M

pH = 7.6, Hardness = 30 mg/L

$[Mg^{2+}] = 1 \times 10^{-4}$ M

It is known that total alkalinity is as follows.

Total alkalinity = $[HCO^{-}_{3}] + [CO^{2-}_{3}] + [OH^{-}] - [H^{+}]$

Since, pH = 7.6. Hence, concentration of hydrogen ions will be calculated as follows.

pH = $-log [H^{+}]$

7.6 = $-log [H^{+}]$

$[H^{+}]$ = antilog (-7.6)

= $2.51 \times 10^{-8}$ M

As, pH + pOH = 14

pOH = 14 - pH

= 14 - 7.6

= 6.4

So, $[OH^{-}] = 10^{-6.4}$

= $3.98 \times 10^{-7} M$

Phenolphthalein alkalinity = $[CO^{2-}_{3}]$

$[HCO^{-}_{3}]$ = Total alkalinity - 2[CO^{2-}_{3}] - [OH^{-}] + [H^{+}][/tex]

= $6.2 \times 10^{-4} - 2(1 \times 10^{-5}) - (3.98 \times 10^{-7}) + (2.51 \times 10^{-8})$

= $5.9 \times 10^{-4} M$

$[Mg^{2+}] = 1 \times 10^{-4} M$ = $24 \times 10^{-4} g/L$

$[Mg^{2+}]$ = 2.4 mg/L

Ratio of molar mass of $Ca^{2+}$ and $[Mg^{2+}]$ with $CaCO_{3}$ is as follows.

$\frac{M_{CaCO_{3}}}{M_{Ca}}$ = $\frac{100}{40}$ = 25

$\frac{M_{CaCO_{3}}}{M_{Mg}}$ = $\frac{100}{24}$ = 4.2

Total hardness = $2.5[Ca^{2+}] + 4.2 [Mg^{2+}]$

$[Ca^{2+}] = \frac{\text{total hardness - 4.2(2.4)}}{2.5}$

= $1.99 \times 10^{-4} mol/L$

$CaCO_{3} \rightarrow Ca^{2+} CO^{2-}_{3}$

$[Ca^{2+}][CO^{2-}_{3}]$ = $(1.99 \times 10^{-4}) \times (1 \times 10^{-5})$

= $1.99 \times 10^{-9}$

$K_{sp}$ of $CaCO_{3}$ = $3.36 \times 10^{-9}$

Since, $[Ca^{2+}][CO^{2-}_{3}]$ > $K_{sp}$

Hence, the water is slightly unsaturated with $CaCO_{3}$ .

Answer from: Quest

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.

Answer from: Quest

its first and third is your answer i did the qustion the fourth isnt right

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Asample of lake water at 25°c is analyzed and the following parameters are found: total alkalinity...

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