Cho 125 ml dung dịch NaOH 2M vào 100 ml dung dịch H2SO4 2M và khuấy đều. Hỏi khi nhúng giấy quỳ tím vào thì giấy quỳ tím chuyển sang màu gì?(dung dịch H2SO4 là 2M lưu ý đó)Help pls.

2 câu trả lời

2NaOH+H2SO4→Na2SO4+H2O

125ml=0.125l

100ml=0.1l

n(NaOH)=CM(NaOH)×V(dd NaOH)=0.25 mol

n(H2SO4)=CM(H2SO4)×V(dd H2SO4)=0.2 mol

ta có:$\frac{n(NaOH)}{2}$ < $\frac{n(H2SO4)}{1}$ 

=>H2SO4 dư

=>dung dịch chỉ còn 3 chất:Na2SO4, H2SO4, H2O

=>quỳ tím hóa đỏ(H2SO4)

Đáp án:

Màu đỏ

Giải thích các bước giải:

\(\begin{array}{l}
2NaOH + {H_2}S{O_4} \to N{a_2}S{O_4} + 2{H_2}O\\
{n_{NaOH}} = 0,25mol\\
{n_{{H_2}S{O_4}}} = 0,2mol\\
 \to \dfrac{{{n_{NaOH}}}}{2} < {n_{{H_2}S{O_4}}}
\end{array}\)

Suy ra có \({H_2}S{O_4}\) dư

Vì dung dịch sau phản ứng có \({H_2}S{O_4}\) dư nên khi cho giấy quỳ tím vào sẽ hóa màu đỏ 

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