英语周报七年级202215期答案

第二节书面表达【写作思路】根据试题要求,考生需要写一篇记叙文,记述身边一位值得尊敬和爱戴的人。首先考生需要介绍自己最尊敬和爱戴的人是谁,简单地介绍一下他(她)。然后,陈述为什么他(她)值得尊敬和爱戴。最后,可以对前文进行一个总结,使文章结构严谨。本文的写作重点在"尊敬和爱戴的原因",考生可围绕这个要点适当拓展,从性格特点、处事风格等方面展开写作。【范文赏读】The most beloved and respected person around me is my teacher, Ms LiThough she has been teaching English for twenty years, she is still passionateabout teaching. She is kind and considerate towards us just like our dear motherWe all respect her because she always tries new ways to make her classes livelyand interesting. Hardworking and knowledgeable, she is one of the best teachersin our school. When we have a problem, we will turn to her for help. She alwaystalks to us patiently and helps us to find a solution. In our eyes, she is not onlyour teacher, but also our best friend. Those are why she deserves our respect【亮点词句】亮点词汇: beloved, respected, be passionate about, be consideratetowards, turn to sb. for help, in one's eyes亮点句式:Why引导的表语从句( why she deserves our respect)

26.(15分)(1)HNNH(1分)HH(2)烧杯、玻璃棒(2分)(3)(2+2H=C+C-+H2O(1分)防止温度过高次氯酸钠分解为氯化钠和氯酸钠(2分)(4)三颈烧瓶(1分)N2H4·H2O+2NaC1O2NaCl+N2↑+3H2O(2分)(5)停止实验,冷却后补加(1分)(6)酸式(1分)当滴入最后一滴碘标准溶液时,溶液由无色变为蓝色,且半分钟内不褪色(2分)75%(2分)【解析】(1)肼的化学式为N2H4,氮原子之间形成对共用电子,电子式为HNNHH(2)配制30%NaOH溶液的实验步骤为计算、称量溶解,所需的玻璃仪器有量筒、烧杯、玻璃棒(3)锥形瓶的作用是吸收氯气,发生反应的离子方程式是Cl2+2OHCO+C+H2O;由题意知,次氯酸钠易分解,故Ⅱ中用冰水浴控制温度在30℃以下,其主要目的是防止温度过高次氯酸钠分解为氯化钠和氯酸钠(4)仪器A为三颈烧瓶;次氯酸钠具有强氧化性,水合肼具有强还原性,若分液漏斗中溶液的滴速过快N2H4·H2O与NaCO反应的化学方程式为N2H4·H2O+2NaCO=2NaCl+N2↑+3H2O,5)液体加热时为防止暴沸,通常加入沸石,若在蒸馏刚刚开始的时候忘记添加沸石,应停止实验,冷却后补加6)碘标准溶液具有氧化性,可以腐蚀橡皮管,应盛放在酸式滴定管中;达到滴定终点的现象是当滴入最后一滴碘标准溶液时,溶液由无色变为蓝色,且半分钟内不褪色。根据关系式:N2H4·H2O~2l2可知,2.000gN2H4·H2O样品中,n(N2H4·H2O)=+×0.02L×0.3000mol·L-125.0m0.03mol,水合肼的质量分数为m×10%=5%

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