A 78.00 g sample of an unknown compound contains 12.40 g of hydrogen. What is the percent by mass of hydrogen in the compound?

In any energy conversion, some of the energy is lost to the environment as question 5 options: electrical energy potential energy sound energy thermal energy

Compare and contrast physical changes with chemical changes.

How many moles are in 7.2 x 10^23 carbon molecules? (*round to the nearest hundredth and include the unit "mol c" after your number) question 6 options: