Chemistry: Which individual elements make up the following common compounds? • caco3 • cacl2 • c3h6o • hcl • ca(oh)2

Which individual elements make up the following

garcia36

22.09.2020

pH=11.45

Explanation:

Hello there!

In this case, since the chemical equation representing the neutralization of the weak base quinine can be written as follows:

$C_{20}H_{24}N_2O_2+HCl\rightarrow C_{20}H_{25}N_2O_2^+Cl^-$

Whereas we have 0.100 moles of the base and those of acid as shown below

$n_{acid}=0.50molHCl/L*0.05000L=0.025molHCl$

Which means that the remaining moles of quinine are:

$n_{C_{20}H_{24}N_2O_2}^{final}=0.100mol-0.025mol=0.075mol$

And the resulting concentration:

$[C_{20}H_{24}N_2O_2]=\frac{0.075mol}{(0.025+0.050)L} =1.00M$

Now, the calculation of the pH requires the pKb of quinine (5.1) as its ionization in water produces OH- ions:

$C_{20}H_{24}N_2O_2+H_2O\rightleftharpoons OH^-++C_{20}H_{25}N_2O_2^+$

And the equilibrium expression is:

$Kb=\frac{[C_{20}H_{24}N_2O_2][C_{20}H_{25}N_2O_2 ^+]}{[C_{20}H_{24}N_2O_2]} \\\\10^{-5.1}=\frac{x^2}{1.00M}\\\\ 7.94x10^{-6}=\frac{x^2}{1.00M}$

Which is solved for x as follows:

$x= \sqrt{7.94x10^{-6}*1.00M}\\\\x=0.00282M$

Which means the pOH is:

pOH=-log(0.00282)=2.55

And the pH:

$pH=14-2.55\\\\pH=11.45$

Regards!

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