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一、选择题 1.10克元素R分别可与氧组成34克氧化物甲、66克氧化物乙,则甲和乙的化学式分别可能是( )。 A.R_2O_3和R_2O_7 B.R_2O和R_2O_3 C.R_2O_3和R_2O_4 D.R_2O_3和R_2O_5 2.甲、乙两种氧化物,甲、乙中R元素的质量百分含量依次为50％和40％,若已知甲是三原子分子,且R与氧的质量比为1:1,则乙的分子式是( )。 A.RO_2 B.RO_3 C.R_2O_3 D.R_2O_5 3.某化合物由a、b两种元素组成,a、b两元素的质量比是3:8,又知a的原子量是b的原子量的0.75倍,则该化合物的分子式可能是
First, the multiple-choice questions 1.10 grams of element R can be composed of oxygen and 34 grams of oxide A, 66 grams of oxide B, then the chemical formula of A and B may be (). A. R_2O_3 and R_2O_7 B.R_2O and R_2O_3 C.R_2O_3 and R_2O_4 D.R_2O_3 and R_2O_5 2. A and B oxides, and the mass percentage of R in A and B is 50% and 40% respectively. Given that A is a triatomic molecule and the mass ratio of R to oxygen is 1:1, the molecular formula of B is (). A.RO_2 B.RO_3 C.R_2O_3 D.R_2O_5 3. The compound consists of a and b elements, the mass ratio of a and b is 3:8, and the atomic mass of a is 0.75 times that of b. , the molecular formula of the compound may be