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Answer:
The first row of elements fits in period <u>6</u>, after the element <u>lanthanum (La)</u>. The second row of elements fits in period <u>7</u>, after the element <u>actinium (Ac). </u>
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<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
Volume= Mass/ Density= 20/184
= 0.108 cubic cm
Hydrogen sulfide gas is reacted with dioxygen gas to produce gaseous sulfur dioxide and water. It is false.
When hydrogen sulfide gas reacts with dioxygen gas, it produces water and solid Sulphur and not gaseous sulfur. The chemical equation of the given substances is :
2H2S + O2 → 2S + 2H20
It is a redox reaction as both Oxidation and reduction happens in it. Oxidation of hydrogen sulphur to sulphur happens and reductions of oxygen to water takes place.
if you need to learn more about chemical reaction of Hydrogen sulfide gas, click here
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