【简答题】木炭在氧气中燃烧比在空气中燃烧得更旺;夏天,将食品放在冰箱里不容易腐烂.说明反应物的浓度和温度对化学反应快慢(反应速率)有影响.那么,浓度和温度是如何影响化学反应速率的? 设计方案:同学们利用双氧水和二氧化锰反应来探究上述问题,设计了下列3组实验.其中二氧化锰的作用是______. 组别 温度 二氧化锰的质量 双氧水的浓度和体积 观察产生气泡的速率 1 室温 0.5g 5%、50mL 反应平稳,有...
【简答题】A The whole family objected when my brother and I said we were going to spend our Christmas holidays abroad.Mother said that as there would be a family reunion party , we would have to be present at a...
【简答题】大肠埃希菌获得半乳糖苷酶基因是通过()|白喉棒状杆菌获得产生白喉毒素的能力是通过()|肉毒梭菌获得产生肉毒毒素的能力是通过()|肺炎链球菌由无荚膜变为有荚膜可以通过()|雌性菌变为雄性菌是通过()A. 转化B. 转导C. 接合D. 性导E. 溶原性转换
【简答题】However important we may regard school life to be, there is always the fact that children spend more time at home than in the classroom. Therefore, the teacher should realize that parents have a great...
【多选题】根据企业所得税的规定,下列各项中,不属于企业所得税纳税人的是( )。