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今年上半年,省教学仪器公司组织的学生实验能力调查中,我主持的那部分初三化学测试中暴露出不少操作错误。现选择其中主要的作一简要分析。一、审题不清。题目要求“将20ml浓食盐水制成饱和溶液。”部分学生将20ml浓食盐溶液倒入蒸发皿,加热蒸去全部溶剂。此举得到的是20ml浓食盐水中所含的食盐固体,而不是饱和溶液。二、仪器的选用或组合不当。如选用10ml量筒量取20ml液体。又如有这样一道试题:“检验铺路石中确含有CO_3~(2-)。”该题提供了需用的和不需用的器材和药品“大试管、小试管、烧杯(100ml)胶头漓管、带直角玻璃管的单孔塞、坩锅钳、药匙、玻璃导管、胶管、镊子、铁架台。稀盐酸、稀硫酸、澄清的石灰
In the first half of this year, during the survey of students’ experimental ability organized by the provincial teaching instrument company, I was exposed to a number of operational errors in the chemical tests of the third-third of the chemistry that I chaired. The main one is selected for a brief analysis. First, the question is unclear. The title requires “saturate a solution of 20 ml of concentrated brine.” Some students poured 20 ml of concentrated salt solution into an evaporating dish and heated to remove all solvents. This resulted in salt solids contained in 20 ml of concentrated brine rather than a saturated solution. Second, improper selection or combination of instruments. If you choose 10ml graduated cylinder take 20ml liquid. In addition, if there is such a test: “The test paving stone contains CO_3~(2-).” This question provides necessary and unnecessary equipment and medicines "large test tube, small test tube, beaker (100ml) plastic head Tubes, single-hole plugs with right-angled glass tubes, crucible pliers, spatula, glass tubes, hoses, tweezers, iron stand, dilute hydrochloric acid, dilute sulfuric acid, clear lime