Determine whether each of the following salts form...

Question

Determine whether each of the following salts form a solution that is acidic, basic, or pH-neutral.a.) Fe(NO3)3b.) C2H5NH3CNc.) RbId.) CH3NH3Cle.) K2CO3

Jules Bruno · Accepted Answer

We're being asked to determine whether each of the following salts form a solution that is acidic, basic, or pH-neutral.Ionic salts are made up of positively charged ion (cation) and a negatively charged ion (anion). To determine if the ionic salt would be acidic, basic, or neutral, we need to identify the acidity or basicity of the cation and anion.For cations:• transition metal▪ charge of +2 or higher → acidic▪ less than +2 → neutral solution• main group metal▪ charge of +3 or higher → acidic▪ less than +3 → neutral solution [readmore]• amines - compounds with only nitrogen or hydrogen (i,e. NH3) or with carbon, nitrogen and hydrogen▪ positive amines → acidicFor anions:• To determine if an anion is basic or neutral you must add an H+ to it.▪ If adding an H+ creates a weak acid → negative ion is basic▪ if adding an H+ creates a strong acid → negative ion is neutrala.) Fe(NO3)3 • Fe3+▪ transition metal → +3 charge▪ charge of +2 or higher → acidic• NO3–▪ add H+:          NO3– + H+ → HNO3▪ HNO3 → strong acid▪ NO3– → neutral• overall▪ acidic + neutral → acidicA Fe(NO3)3 solution is acidic.b.) C2H5NH3CN• CH3NH3+▪ polyatomic ion → positively charged amine → acidic• CN–▪ add H+:          CN– + H+ → HCN▪ HCN → weak acid▪ CN– → basicSince CH3NH3+ is acidic and CN– is basic, we have to compare their Ka and Kb in order to determine which ion would have a greater influence on the acidity or basicity of the solution made.• We have to calculate the Ka of CH3NH3+ and Kb of BrO-• CH3NH3+ is the conjugate acid of CH3NH2, so we can calculate Ka of CH3NH3+ from the Kb of CH3NH2CH3NH2 + H2O ⇌ CH3NH3+ + OH- (weak base) (acid) (conjugate acid) (conjugate base)• CN– is the conjugate base of HCN, so we can calculate the Kb of CN– from the Ka of HCN.    HCN + H2O ⇌ CN– + OH(weak base) (acid) (conjugate acid) (conjugate base) Ka and Kb are connected by the autoionization constant of water (Kw) by the following equation:Kw=Ka·Kb Kw is a constant and is temperature dependent. We will assume that the temperature is at 25°C (unless stated otherwise) and the value of Kw at this temperature is:Kw = 1.0x10-14             @ 25°CCalculate Ka of NH4+:Kb (CH3NH3+) = 4.4×10–4Kw = 1.0x10–14KwKb=Ka·KbKbKa=KwKbKa=1.0×10-144.4×10-4Ka = 2.2727×10–11Calculate Kb of CN-:Given: Ka (HCN) = 6.2×10–10Kw = 1.0x10–14KwKa=Ka·KbKaKb=KwKaKb=1.0×10-146.2×10-10Kb = 1.6129×10–5Comparing Ka of CH3NH3+ and Kb of CN–:• K­a of CH3NH3+ (2.27×10–11) < Kb of CN– (1.61x10–5)• CN– (basic ion) will have a greater influence on the solutionA C2H5NH3CN solution is acidic.c.) RbI• Rb+▪ main group metal → group 1A → +1 charge▪ less than +3 → neutral• I–▪ add H+:          I– + H+ → HI▪ HI → strong acid▪ I– → neutral• overall▪ neutral + neutral → pH-neutralA RbI solution is pH-neutral.d.) CH3NH3Cl• CH3NH3+▪ polyatomic ion → positively charged amine → acidic• Cl–▪ add H+:          Cl– + H+ → HCl▪ HCl → strong acid▪ Cl– → neutral• overall▪ acidic + neutral → acidicA CH3NH3Cl solution is acidic.e.) K2CO3• K+▪ main group metal → group 1A → +1 charge▪ less than +3 → neutral• CO32– → polyatomic ion▪ add H+:          CO32– + H+ → HCO3–▪ HCO3– → weak acid▪ CO3– → basic• overall▪ neutral + basic → basicA K2CO3 solution is basic.

Problem: Determine whether each of the following salts form a solution that is acidic, basic, or pH-neutral.a.) Fe(NO3)3b.) C2H5NH3CNc.) RbId.) CH3NH3Cle.) K2CO3

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Problem: Determine whether each of the following salts form a solution that is acidic, basic, or pH-neutral.a.) Fe(NO3)3b.) C2H5NH3CNc.) RbId.) CH3NH3Cle.) K2CO3

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