What is the mass number of an atom which contains 21 electrons, 21 protons, and 24 neutrons?

Explain why the chemical formulas of ionic compounds are usually the same as their empirical formulas.

When an object is lifted 12 meters off the ground, it gains a certain amount of potential energy. If the same object is lifted 24 meters off the ground, its potential energy is which of the folowing? The same. B. three times as much. C.

What is the molar mass of Mg (NO3) 2? Explain how you calculated this value.

Describe the motion of the gas particles.

A rigid cylinder with a movable piston contains a sample of hydrogen gas At 330k the sample has a pressure of 150 kpa and a volume of 3.50l what is the volume of this sample at STP

Which statement best explains why elements are matter? An element is a physical substance that has mass and takes up space. Elements are pure substances that cannot be divided chemically. Each element is a pure substance composed of one type of atom.

Which of the following best describes what causes the phases of the moon? The alignment of the sun, Earth, and moon The speed of the moon around the Earth The speed of the Earth around the sun The alignment of the planets

At which temperature would atoms of a He (g) sample have the greatest average kinetic energy? (1) 25°C (3) 273 K (2) 37°C (4) 298 K

In the reaction, HCl + H2O produces H3O + Cl, what is the conjugate acid

Draw the curved arrow mechanism for the conversion of aniline into benzenediazonium ion, and draw the final product that forms after the benzenediazonium ion is treated with