What is the half-life of an isotope if 62.5 g of a 500. g sample remains after 18 years? PLS ASAP I NEED THIS

Consider the balanced equation below. n2h4 + 2h2o2 n2 + 4h2o what are the mole ratios of hydrazine (n2h4) to hydrogen peroxide (h2o2) and hydrazine to water? 1: 2 and 1: 4 1: 3 and 1: 4 1: 2 and 3: 5 1: 3 and 3: 5

Dying the folding patterns of protein molecules can microbiologists better understand cellular processes as well as some diseases, such as alzheimer’s, that are caused by proteins that have misfolded. the folding of these complicated molecules can be simulated on computers, but it takes a lot of processor power and time for even expensive supercomputers to do this. a group of researchers at stanford university developed software that can be used to distribute the processing of data to anyone who is willing to donate time on their idle personal computers. as a result, the researchers have been able to achieve protein-folding simulations that are far better than those other computing methods have done. which statement best describes the work of these researchers? the work is not scientific because the data are not processed in one location. the work is not scientific because the simulations are not reproducible. the researchers applied creativity to solve a problem in running an experiment. the researchers used only well-established scientific techniques.

The reaction q+r2=r2q is found to be first order in r2 and