The primary greenhouse gases<span> in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Without </span>greenhouse gases<span>, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).</span>
the best answers its A. Maxwell I just took the the test
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The answer is 69.048%.
Mass of potassium dichromate (K₂Cr₂O₇) is 294 g, which is a 100%.
Given mass of chromium is 52 g. So, the mass percent of chromium in the compound is 17.687%:
52 g : x% = 294 g : 100%
x = 52 ÷ 294 × 100 %
x = 17.687%
Given mass of potassium is 39 g. <span>So, the mass percent of potassium in the compound is 13.265%:
39 g : x% = 294 g : 100%
x = </span>39 ÷ <span>294 × 100 %
x = 13.265%
Therefore, </span>the mass percent of oxygen in the compound is <span>69.048%:
100% - </span>17.687% - <span>13.265% = 69.048%.</span>
Explanation:
1 mole of a gas has 22.4 L of volume at STP. Therefore, 0.5 mol of H2 has 0.5 x 6.022 x 1023 = 3.011 x 1023 molecules. Hence, the number of moles, molecules and atoms present in 11.2 liters of H2 at STP are 0.5 , 3.011 x 1023 and 6.022 x 1023 respectively.
