Why would the percentage yield be less then 100 percent when collecting gases​

In the reading, yao chen-yuan describes traveling to deliver a message. why was he willing to risk danger to travelto tientsin? he wanted to the boxers with their cause

What is the mass defect of a mole of nuclei with 1.8 x 10^15 j/mol binding energy?

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