How do you find the mass of an object?

For the reaction shown, calculate how many moles of no2 form when each of the following completely reacts. 2n2o5(g)→4no2(g)+o2(g) part a 1.0 mol n2o5 express your answer using two significant figures. nothing mol m o l request answer part b 5.4 mol n2o5 express your answer using two significant figures.

Assume that 13.5 g solid aluminum (al) react with hcl to produce solid aluminum chloride (alcl3) salt and gaseous hydrogen (h2) at standard temperature and pressure.

When casey looks at a cd or dvd she notices that there is a rainbow pattern that is created by the light. she became curious and shone light directly at it and a pattern was created on the wall. what is the cause of this pattern?