The element Europium exists in nature as two isotopes: 151Eu, which has a mass of 150.9196amu, and 153Eu, which has a mass of 152.9209amu. Calculate the percent abundance of each isotope using 4 significant figures in your answers.

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Agroup of students is studying convection current. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other is in an area with warm air. after 10 minutes, the balloon are released from a height of 1 meter. which of the following to the students most likely observe? a) the warm balloon expands and rises. the cold balloon shrinks and sinks b) the balloon both rise. the cold balloon is larger than the warm balloon c) the cold balloon expands and rises. the warm balloon shrinks and sinks d) the balloon rise at the same rate. both balloons are the same size

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