室温下,将0.20(mol/L)的(HCl)溶液与0.20(mol/L)的(NH)_3cdot(H)_2(O)溶液等体积混合(忽略混合溶液体积变化),(已知: (NH)_3的K_b=1.8times10^-5; lg 7.5=0.88; lg 5.6=0.75; lg 2=0.30; lg 1.06=0.02; sqrt(0.56)=0.75; sqrt(1.12)=1.06)该混合溶液的(pH)为()A. 1.00B. 10.00C. 5.12D. 4.98E. 7.00

室温下,将$0.20\text{mol/L}$的$\text{HCl}$溶液与$0.20\text{mol/L}$的$\text{NH}_3\cdot\text{H}_2\text{O}$溶液等体积混合(忽略混合溶液体积变化),(已知: $\text{NH}_3$的$K_b=1.8\times10^{-5}$; $\lg 7.5=0.88$; $\lg 5.6=0.75$; $\lg 2=0.30$; $\lg 1.06=0.02$; $\sqrt{0.56}=0.75$; $\sqrt{1.12}=1.06)$该混合溶液的$\text{pH}$为()

A. 1.00

B. 10.00

C. 5.12

D. 4.98

E. 7.00