Chemistry, 06.12.2020 14:10 megamorph

3. If x electrons are needed to displace 108 g silver from a solution which contains Ag ions, how many electrons are needed to displace 9 g of aluminium from a solution which contains
Al ions?

[Relative atomic mass Al, 27; Ag, 108]
A X
B 3x
C 4x
D 9x

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Answer from: Fiwui

Choice A. electrons would be required for displacing $9\; \rm g$ of aluminum from a solution of $\rm Al^{3+}$ ions.

Assumption: by " $\rm Ag$ ions" the question meant $\rm Ag^{+}$ with a charge of on each ion.

Explanation:

The question states that the relative atomic mass of $\rm Ag$ is 108 . In other words, each mole of

Therefore, that $108\; \rm g\!$ of silver that were formed would contain $1\; \rm mol$ of silver atoms.

Metallic silver would precipitate out of this $\rm Ag^{+}$ solution only after these ions are turned into $\rm Ag$ atoms.

One $\rm Ag^{+}$ ion carries one unit of positive electrical charge. On the other hand, each $e^{-}$ carries one unit of negative electrical charge.

Therefore, each $\rm Ag^{+}\!$ ion will need to gain one electron to form a neutral $\rm Ag$ atom.

${\rm Ag^{+}}\; (aq) + e^{-} \to {\rm Ag}\; (s)$ .

At least $1\; \rm mol$ of electrons would be required to turn $1\; \rm mol\!$ of $\rm Ag^{+}$ ions into that $1\; \rm mol\!\!$ of silver atoms (which have a mass of $108\; \rm g\!$ .)

Hence, $x = 1\; \rm mol$ .

Unlike $\rm Ag^{+}$ ions, each aluminum ion $\rm Al^{3+}$ carries three units of positive electrical charge. That is three times the amount of charge on one $\rm Ag^{+}\!$ ion. Therefore, three electrons will be required to turn one $\rm Al^{3+}\!$ ion to an $\rm Al$ atom.

${\rm Al^{3+}}\; (aq) + 3\, e^{-} \to {\rm Al}\; (s)$

The question states that the relative atomic mass of $\rm Al$ is . Therefore, each mole of $\rm Al\!$ atoms would have a mass $27\; \rm g$ . There would be $\displaystyle \frac{9\; \rm g}{27\; \rm g \cdot mol^{-1}} = \frac{1}{3} \; \rm mol$ of atoms in that $9\; \rm g$ of $\rm Al\!\!$ .

It takes $3\; \rm mol$ of electrons to turn one mole of $\rm Al^{3+}$ ions to one mole of $\rm Al$ atoms. Hence, $\displaystyle \frac{1}{3}\times 3\; \rm mol = 1\; \rm mol$ of electrons would be required to produce that $\displaystyle \frac{1}{3}\; \rm mol$ of $\rm Al\!$ atoms (which has a mass of $9\; \rm g$ ) from $\rm Al^{3+}\!$ ions.

That corresponds to the first choice, electrons.

Answer from: Quest

answer: option (4) is the correct answer.

explanation:

areas which are at low altitudes and near the equator tend to receive direct sunlight from the sun. hence, heat energy or radiations from the sun make these areas warmer and they have warmest water.

whereas areas which are at high altitudes and away from the equator do no receive direct sunlight. hence, no direct contact from the sun makes these regions colder and thus, they have colder water.

thus, we can conclude that the statement areas at low latitudes near the equator have the warmest water because they receive the most direct sunlight best explains the relationship between an area's geography and the temperature of its surface water.

Answer from: Quest

fe 55.85 g/mol and h2o 18.02 g/mol.

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3. If x electrons are needed to displace 108 g silver from a solution which contains Ag ions, how m...

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