Acids, Equilibrium, and Qualitative Analysis in Chemistry

This set of flashcards covers key concepts related to acids, equilibrium behavior, qualitative analysis, and indicators in chemistry.

Why are $HNO_3$ and $HI$ both strong acids in water, but $HNO_3$ is a weak acid while $HI$ remains strong in acetic acid?

Because acetic acid is less basic than water; it does not accept protons as readily, so $HNO_3$ does not completely dissociate in it.

Why is the hydrated ion $[Cr(H_2O)_6]^{3+}$ considered acidic in solution?

The high positive charge of the metal ion draws electron density away from the $O-H$ bonds of the water ligands, allowing the ion to easily lose a proton.

Why is sulfuric acid ($H_2SO_4$) a stronger acid than phosphoric acid ($H_3PO_4$)?

Sulfuric acid has two terminal oxygen atoms attached to the central atom, whereas phosphoric acid has only one.

Why is $H_2S$ a stronger acid than $H_2Se$?

Because Selenium is less electronegative than sulfur, affecting the stability and polarity of the bond.

When determining the pH of a weak acid, when must the change in acid concentration (the D-xD in ICE tables) be strictly considered?

It must be considered if the acid is more than 5% dissociated.

Is an aqueous solution of ammonium sulfide acidic, basic, or neutral?

It is basic.

Is a solution of ammonium chloride acidic, basic, or neutral?

It is acidic.

Which of the following salts would yield an acidic solution: $Na_3PO_4$, $Fe(NO_3)_3 imes 6H_2O$, $NaCH_3CO_2$, or $Na_2SO_4$?

$Fe(NO_3)_3 imes 6H_2O$.

In the qualitative analysis of metal ions, why might a student find Group-1 cations in their Group-2 precipitate?

This happens if the student skips the removal of Group-1 cations (selective precipitation) before adding $H_2S$.

What is the specific purpose of sodium thiosulfate in processing photographic film?

The thiosulfate ion increases the solubility of silver bromide by complexing with the silver ion.

Which salt's solubility would NOT depend strongly on the pH of the solution: $Co_2S_3$, $Ag(CH_3CO_2)$, $Ca_3(PO_4)_2$, or $PbI_2$?

$PbI_2$.

For which of the following species is solubility least affected by the formation of ion pairs: $PbCO_3$, $NaI$, $FePO_4$, or $BaSO_4$?

$NaI$.

Why would methyl red ($pK_{in} = 5.00$) be unusable for the titration of a weak acid ($pK_a = 4.5$) with $NaOH$?

The indicator would change color before the equivalence point is reached.

What type of forces are responsible for the phenomenon of incomplete dissociation?

Electrostatic attractions.