A mixture of gases contains 8.00 g of He, 29.96 g of Ar, and 48.00 g of O2. What is the mole fraction of He in this mixture

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Hey guys so i need to know what is _nh3+> nh4oh ~chemistry~

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.