Đáp án:
53)
C
54)
A
55)
B
56)
B
57)
A
58)
C
Giải thích các bước giải:
\(\begin{array}{l}
53)\\
{{\bar M}_{Cu}} = \dfrac{{63 \times a + 65 \times b}}{{100}} = 63,54\\
\Rightarrow \dfrac{{63 \times a + 65 \times (100 - a)}}{{100}} = 63,54\\
\Rightarrow a = \dfrac{{6500 - 6354}}{2} = 73\% \\
\Rightarrow b = 100 - 73 = 27\% \\
54)\\
{{\bar M}_B} = \dfrac{{11 \times a + 10 \times b}}{{100}} = 10,8\\
\Rightarrow \dfrac{{11 \times a + 10 \times (100 - a)}}{{100}} = 10,8\\
\Rightarrow a = \dfrac{{1080 - 1000}}{1} = 80\% \\
55)\\
\% _{29}^{63}Cu = \dfrac{{105}}{{105 + 245}} \times 100\% = 30\% \\
\% _{29}^{65}Cu = 100 - 30 = 70\% \\
{{\bar M}_{Cu}} = \dfrac{{63 \times 30 + 65 \times 70}}{{100}} = 64,4\\
56)\\
{{\bar M}_{Cl}} = \dfrac{{35 \times 75,77 + 37 \times 24,23}}{{100}} = 35,48\\
57)\\
{{\bar M}_{Cu}} = \dfrac{{63 \times 73 + 65 \times 27}}{{100}} = 63,54\\
{m_{Cu}} = 63,54 \times 0,5 = 31,77g\\
58)\\
{{\bar M}_{Br}} = \dfrac{{79 \times a + 81 \times b}}{{100}} = 79,91\\
\Rightarrow \dfrac{{79 \times a + 81 \times (100 - a)}}{{100}} = 79,91\\
\Rightarrow a = \dfrac{{8100 - 7991}}{2} = 54,5\% \\
\Rightarrow b = 100 - 54,5 = 45,5\%
\end{array}\)
