25℃时，某烧杯盛有饱和的NH4Cl溶液，其底部有少量未溶解的NH4Cl_爱下问搜题

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问题选择题

25℃时，某烧杯盛有饱和的NH₄Cl溶液，其底部有少量未溶解的NH₄Cl晶体，若将温度升高到40℃，使其变成不饱和溶液，则溶液中溶质的质量分数（　　）

A．变小

B．变大

C．不变

D．无法判断

答案

25℃时，饱和的NH₄Cl溶液，其底部有少量未溶解的NH₄Cl晶体（没有溶解不算是溶质），升高温度，氯化铵的溶解度增大，氯化铵继续溶解，溶质的质量加大，而溶剂的量不变，溶液中溶质的质量分数变大．

故选B．

单项选择题

(66) is a one-way function that takes an arbitrarily long piece of plaintext and from it computes a fixed,length bit string. (67) is a protocol that most USENET machines now use it to allow news articles to propagate from one machine to another over a reliable connection. (68) is an approach preferred by cable TV providers. In this solution the fiber terminates at an opt~electrical converter and the final segment is a shared coaxial cable. (69) is a device used to connect two separate network that use different communication protocol. (70) is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

A．Router

B．Gateway

C．Bridge

D．hub

判断题

在一个心动周期中，心室收缩期较舒张期时间长。