If the mass of a test tube with copper oxide before heating is 30g and the mass of the test tube with copper after heating is is 20g, what was the mass of the oxygen heated off? Chemistry Thermochemistry Thermochemistry of Phase Changes 1 Answer S.S Sep 24, 2016 #10# grams Explanation: #30 - 20 = 10# Answer link Related questions How much energy is required to convert 100.g of ice at 0.00 °C to water vapor at 100.00 °C? How do you calculate the heat required to melt 15 kg of silver? When a liquid loses energy, will it change into a gas or a solid? What is the name of the process when a liquid changes into a gas? How much energy is needed to convert 23.0 grams of ice at -10.0°C into steam at 109°C? What amount of ice must be added to 540.0 g of water at 25.0 °C to cool the water to 0.0 °C and... How can I find specific heat in thermochemistry of phase of changes? How much energy is required to convert 100.0 g of water at 20.0 °C completely to steam at 100.0 °C? Calculate the number of joules given off when 32.0 grams of steam cools from 110.0 °C to ice at -40.0 °C. How many joules of heat are needed to change 50.0 grams of ice at -15.0 °C to steam at 120.0 °C? See all questions in Thermochemistry of Phase Changes Impact of this question 2145 views around the world You can reuse this answer Creative Commons License