A chemist needs 0.550 mol selenium for a reaction. What mass of selenium should a chemist use? *show work and giving brainliest*

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)

Isopropyl alcohol, (ch3)2choh, is a common solvent. determine the percent by mass of hydrogen in isopropyl alcohol. a) 6.71% h b) 13.4% h c) 25.0% h d) 53.3% h

Which statement would indicate the presence of an acid