Write Balanced net ionic equations for the reactions between (if no reaction put

Question

Write Balanced net ionic equations for the reactions between (if no reaction put NR): Show state of of products "l", "aq", "s" or "g" a) NH_4^+ (aq) + OH^- (aq) rightarrow b) Ca^2+ (aq) + CO^2+_3 (aq) rightarrow c) K^+ (aq) + SO^2-_4 (aq) rightarrow d) BaCO_3 + H^+ (aq) (excess) rightarrow e) Fe^3+ (aq) + OH^- (aq) rightarrow Calculate pH of a buffer solution prepared by mixing 1000 0mL of 0.100 M NH_3 with 10.800 g of solid NH_4Cl (molar mass-53.50 g/mol). Calculate pH of the buffer from problem 2 after addition to buffer 2.00g of HCl(g) (molar mass-36.50g/mol) Net ionic equation must be given. 4. 0 120M solution of monohydroxo base has the pH vaiue of 10.10. Calculate the value of K_b (base ionization constant).

Explanation / Answer

3) first calculate the molaeity of NH4Cl and HCl

[NH4Cl] = (10.8 / 53.50) (1000 / 1000)

[NH4Cl] = 0.202 M

[HCl] = (2 / 36.50) (1000 / 1000)

[HCl] = 0.055 M

after addition of HCL to the buffer following reaction takes place

NH3 + HCl ------------> NH4Cl

net ionic reaction as follows

NH3 + H+  ----> NH4+

so by addition of HCl concentration of NH3 decreases

NH4Cl will increase

[NH4Cl] = 0.202 + 0.055 = 0.257 M

[NH3] = 0.1 - 0.055 = 0.045 M

pOH = pKb + log [NH4Cl] / [NH3]

pKb = 4.74 for NH3

pOH = 4.74 + log [0.257]/[0.045]

pOH = 5.50

pH = 14 - 5.50

pH = 8.50

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