LARC CHEM 1C Midterm 2

Definitions of Acids/Bases

100

What is a Bronsted acid?

Proton donors (They release H{1+} in water)

200

What is the conjugate base of H2O?

the hydroxide ion (a.k.a. OH{1-})

300

The bicarbonate ion (HCO3{1-}) is an example of an amphoteric compound. What is its conjugate acid? What is its conjugate base?

Conjugate acid: H2CO3; Conjugate base: CO3{2-}

400

What are the 7 strong acids?

HCl, HBr, HI, HNO3, HClO4, HClO3, H2SO4

500

Are highly-charge metal cations (e.g. Al{3+}, Cu{2+}, Fe{3+}, etc.) Lewis acids or Lewis bases?

Lewis acids

ICE Table Questions

100

What is the Ka expression of the reaction

HA ⇄ H{1+} + A{1-}

Ka = [H+][A-]/[HA] (concentrations at equilibrium)

200

Write the base dissociation reaction for HSO4{1-} in water.

HSO4{1-} + H2O ⇄ H2SO4 + OH{1-}

300

Find the Kb of NH3 given the pKa of NH4{1+} is around 9.

pKa(NH4+) + pKb(NH3) = 14

pKb(NH3) = 14 - 9 = 5

Kb = 10^(-pKb) = 10^(-5)

400

Use the "x is little" approximation to simplify this equation:

Ka = (0.10 + x)(x)/(0.10 - x)

Ka = 0.10x/0.10 = x

500

Setup the ICE table for 0.1 M of HA by itself

Initial: [HA] = 0.1 M; [H+] = [A-] = 0

Change: [HA] = - x; [H+] = [A-] = + x

Equil: [HA] = 0.1 - x; [H+] = [A-] = x

Salts, Ions, Buffers, Titrations

100

Which of the following cations WILL hydrolyze water?

Na{1+}, Ca{2+}, Fe{2+}, Ba{2+}

Fe{2+}

200

Which of the following anions will NOT hydrolyze water?

HCOO{1-}, C7H5O2{1-}, ClO3{1-}, CN{1-}

ClO3{1-}

300

I want to make a buffer with acetic acid/vinegar (CH3COOH). What is a salt of its conjugate base?

Any are okay: CH3COONa, CH3COOK, CH3COOLi

400

What are the 8 strong bases?

NaOH, LiOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

500

Strong acid (HCl) is slowly added to weak base (NH3). What compound largely present at the equivalence point?

NH4{1+}