AD
分析:根據(jù)相對分子的質(zhì)量為組成分子的各原子的相對原子質(zhì)量之和,
(1)如x為奇數(shù)時(shí),氧化物化學(xué)式為 R
2O
x,硫酸鹽的化學(xué)式為 R
2(SO
4)
x;
(2)x為偶數(shù)時(shí),氧化物化學(xué)式為 R
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,硫酸鹽的化學(xué)式為 R(SO
4)
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;
依據(jù)相對分子質(zhì)量與化學(xué)式的關(guān)系解答出x的值即可.
解答:設(shè)該元素化合價(jià)為+x價(jià),相對原子質(zhì)量為y.
(1)如x為奇數(shù)時(shí),氧化物化學(xué)式為 R
2O
x,硫酸鹽的化學(xué)式為R
2(SO
4)
x,據(jù)題意有
2y+16x=a,2y+96x=b; 解得x=
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.
(2)x為偶數(shù)時(shí),氧化物化學(xué)式為R
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,硫酸鹽的化學(xué)式為R(SO
4)
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,據(jù)題意有
y+16×
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=a,y+96×
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=b;解答
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.
故選AD.
點(diǎn)評:本題不僅考查了化學(xué)式的書寫及意義,而且考查了相對分子質(zhì)量的概念和常見元素(即氧元素的化合價(jià))及其應(yīng)用等;綜合性較強(qiáng),解答本題時(shí)首先要理清解題思路,然后大膽地設(shè)未知量,列式求解即可.