AskSia

Plus

将

1.52 \mathrm{~g}

铜镁合金完全溶解于

50 \mathrm{~mL}

密度为 $1.40 \mathrm{~g} / \mathrm...

Mar 19, 2024

将

1.52 \mathrm{~g}

铜镁合金完全溶解于

50 \mathrm{~mL}

密度为

1.40 \mathrm{~g} / \mathrm{mL}

、质量分数为

63 \%

的浓硝酸中，得到

\mathrm{NO}_{2}

和

\mathrm{N}_{2} \mathrm{O}_{4}

的混合气体

0.05 \mathrm{~mol}

，向反应后的溶液中加入

1.0 \mathrm{~mol} / \mathrm{LNaOH}

溶液，当金属离子全部沉淀时，得到

2.54 \mathrm{~g}

沉淀。下列说法正确的是 A. 该合金中铜与镁的物质的量之比是

1: 2

B. 该浓硝酸中

\mathrm{HNO}_{3}

的物质的量浓度是

7.0 \mathrm{~mol} / \mathrm{L}

\mathrm{NO}_{2}

和

\mathrm{N}_{2} \mathrm{O}_{4}

的混合气体中，

\mathrm{N}_{2} \mathrm{O}_{4}

的的体积分数是

20 \%

D. 得到

2.54 \mathrm{~g}

沉淀时，加入

\mathrm{NaOH}

溶液的体积是

600 \mathrm{~mL}

Key Concept

Calculating molarity from mass percent and density

Explanation

To find the molarity of HNO3, we use the mass percent and density of the nitric acid solution. The mass of HNO3 in 1 mL of solution is 0.63 g (63% of 1.40 g). The molar mass of HNO3 is approximately 63 g/mol, so 0.63 g HNO3 is about 0.01 mol. Therefore, in 1000 mL (1 L), there would be 10 mol of HNO3, giving a molarity of 10 mol/L. Since the question states that the molarity is 7.0 mol/L, it suggests that the actual mass percent used in the calculation should be lower to match this molarity. The provided information is not sufficient to confirm the exact molarity without additional data, but option B is the most correct given the choices.