问题 选择题

可以判定某酸(HA)是强电解质的事实是(  )

A.该酸加热至沸腾不分解

B.0.01 mol·L-1该酸的pH=2

C.该酸可以溶解Cu(OH) 2

D.该酸与CaCO3反应放出CO2

答案

答案:B

题目分析:强电解质完全电离,不存在电离平衡,B中氢离子浓度和该一元酸的浓度相等,说明完全电离,不存在电离平衡,所以选项B正确;A是酸的稳定性,C和D都是表现酸性,但并能确定是否是强电解质,答案选B。

点评:弱电解质的证明,是基于与强电解质对比进行的。弱电解质与强电解质最大的区别就是弱电解质存在电离平衡,而强电解质不存在电离平衡。因此只要证明有电离平衡存在,就证明了弱电解质。

选择题
单项选择题

Questions from 31 to 35 are based on the following passage: A garment label is more than just a piece of fabric. It is something that draws the attention of customers to the garment. In today’s times, labels actually help in selling a garment. Customers decide whether to buy a piece of apparel or not on the basis of its label. Labels communicate to the customer what types of materials have been used in making the garment. Different manufacturers use their own special type of labels to create their own distinct identity. A label might be custom-made by a manufacturer to make it unique. Beautiful, customized labels add to the beauty and style of the garment.Each brand produced by the manufacturer is usually distinguishable on the basis of a special symbol, color or word. This is reflected through the label. Garment labels can be made using several fabrics, in different types of finishes and can be attached to the garment in different styles. The fabrics that are commonly used in the preparation of labels are satin, damask, semi-damask and taffeta. In some cases, cotton, canvas and felt are also used in making labels. Satin is the most used fabric in preparing labels. Leather labels are generally used in case of jeans and pants. PVC labels are used in pants and bags. Satin is soft on the skin and looks very pretty initially. However, it is not one of the best fabrics to be used in labels because it is very thin and can snag easily. Labels made using taffeta are stiffer than those of satin and do not snag as easily. However, taffeta labels can irritate the skin of the customers. Damask and semi-damask are ideal fabrics for making labels. Damask labels are soft even after finishing and do not cause any irritation to the customer. Semi-damask is similar to damask in feel, but it costs lesser than damask.

The most used fabric adopted in the labels is().

A.felt

B.semi-damask

C.satin

D.leather