What defines an exothermic reaction?

O A. A reaction that needs heat added

O B. A reaction that possesses enthalpy

O c. A reaction that relies on collisions

O D. A reaction that produces heat

What is the volume of an object whose dimensions are 5.54 cm, 10.6 cm, and 199 cm?

The radioisotope radon-222 has half-life of 3.8 days. how much of a 73.9-g sample of radon-222 would be left after approximately 23 days?

What does burning bread in a toaster demonstrate? (a) Energy can create a change. (b) Energy can cause motion. (c) A toaster creates its own energy. (d) A toaster is needed to burn bread.

A hydrocarbon, subjected to elemental analysis, was found to contain 79.89 % carbon and 20.11 % hydrogen by mass. What is the empirical formula of the hydrocarbon?

What are repelled in the VSEPR theory? A. Other molecules B. Opposite charges C. Protons in nuclei D. Electron pairs

How many liters of radon gas would be in 3.43 moles at standard temperature and pressure (273 K and 100 kPa) ? A. 100 L B. 76.83 L C. 6.53 L D. 6.99 L

Which of the following equations describes a single-replacement reaction? A. 2N2O5 (g) = O2 (g) + 4NO2 (g) B. 2Na (s) + Cl2 (g) = 2NaCl (s) C. Cl2 (g) + 2Kl (s) = 2KCl (s) + l2 (g) D. H2 (g) + Br2 (g) = 2HBr (g)

What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.50*1015Hz1.50*1015Hz? Express your answer in joules to three significant figures.

Using your knowledge of symbols, determine which compound listed must contain both copper and oxygen. a. glucose, C6H12O6 b. chalcopyrite, CuFeS2 c. malachite, Cu2CO3 (OH) 2 d. calcite, CaCO3

Molecules move most slowly in: solids liquids gases compounds