18a - Lewis theory and acid calculations

Which is an example of a Lewis base?

• an electrophile

• BF₃

• CH₄

• a nucleophile

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Which statements are correct?

I. Lewis bases can act as nucleophiles.

II. Electrophiles are Lewis acids.

III. Lewis acids are electron pair acceptors.

• I and II only

• I and III only

• II and III only

• I, II and III

Which type of bond is formed when a Lewis acid reacts with a Lewis base?

• Covalent
• Dipole-dipole
• Double
• Hydrogen

Which compound forms an acidic solution when dissolved in water?

• FeCl₃

• CH₃NH₂

• NaNO₃

• Na₂CO₃

In which reaction does H₂O act as a Lewis base but not as a Brønsted–Lowry base.

• H₂O + NH₄⁺ → H₃O⁺ + NH₃

• H₂O + CaO → Ca²⁺ + 2OH⁻

• H₂O + [Fe(H₂O)₆]³⁺ → Fe[(OH)(H₂O)₅]²⁺ + H₃O⁺

• 6H₂O + [Ni(NH₃)₆]²⁺→6NH₃ + [Ni(H₂O)₆]²⁺

The forward reaction of this equilibrium is endothermic. H₂O(l) ⇌ H⁺ (aq) + OH⁻(aq) Kw = 1.0×10⁻¹⁴ at 25 ^∘C What is correct about water at 50 °C?

• [H⁺] > [OH⁻]

• [H⁺] < [OH⁻]

• pH < 7.0

• pH = 7.0

Tags

NGSS.HS-PS1-5

Which equation represents a reaction for which a base dissociation constant expression, K_b, can be written?

• CH₃COOH(aq) + NH₃(aq) ⇌ CH₃COO⁻(aq) + NH₄⁺(aq)

• HF(aq) ⇌ H⁺ (aq) + F⁻(aq)

• HCN(aq) + OH⁻(aq) ⇌ CN⁻(aq) + H₂O(l)

• NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)

The strengths of four acids are: glycine pK_a = 9.87 chloroethanoic acid K_a = 1.38×10⁻³ phenol Ka = 1.00×10⁻¹⁰ butanoic acid pK_a = 4.82 What is the order of increasing acid strength?

• chloroethanoic acid < butanoic acid < phenol < glycine

• glycine < phenol < chloroethanoic acid < butanoic acid

• phenol < chloroethanoic acid < butanoic acid < glycine

• phenol < glycine < butanoic acid < chloroethanoic acid

Which compound will produce an aqueous solution which has a pH greater than 7?

• CuSO₄

• FeCl₃

• Na₂CO₃

• NH₄NO₃

What is the approximate pH of a 0.01 moldm⁻³ ammonia solution?

• 2

• More than 2 but less than 7

• More than 7 but less than 12

• 12