【简答题】铬(Cr)属于重金属元素,含铬的废水和废渣在排放前必须经过相应处理并达到相关的安全标准。 (1)铬的原子序数为24,铬位于周期表中第___周期第___族。 (2)铬元素常以Cr 2 O 7 2- 的形式存在于酸性废水中,常用硫酸亚铁将其还原为Cr 3+ ,再用沉淀法分离除去。已知:当1×10 -6 mol.L -1 ≤c(OH -)<1×10 -4 mol.L -1 时,则发生的反应的离子方程式为...
【单选题】Part II Vocabulary Section A Choose the correct answer to fill in the blank in each sentenceWe made an ______ of everything in the apartment.
【单选题】Part II Vocabulary checkSection A Choose the correct answer to fill in the blank in each sentence.The strategy was to sell the company’s own __________ roasted coffee.
【单选题】Part II Vocabulary & Structure Section A 16. ... Let’s have Mexican food. ... ______________
【单选题】Part II Vocabulary & Structure Directions : This part is to test your ability to construct correct and meaningful sentences. It consists of 2 sections. 25 、 Let's find people with computer skills to _...
【简答题】磷是地壳中含量较为丰富的非金属元素,主要以难溶于水的磷酸盐如Ca 3 (PO 4 ) 2 等形式存在。它的单质和化合物在工农业生产中有着重要的应用。 (1)白磷(P 4 )可由Ca 3 (PO 4 ) 2 、焦炭和SiO 2 在一定条件下反应获得。相关热化学方程式如下: 2Ca 3 (PO 4 ) 2 (s)+10C(s)=6(s)+P 4 (s)+10CO(g) ΔH 1 =+335...
【单选题】Part II Vocabulary and Structure (10 minutes) Section A 25. Let’s find people with computer skills to ____ a team for the project.