In chemical reactions, the substances present at the start of the reaction are called, and the substances produced are called

A 65kg driver is poised at the edge of a 10.0m high platform. Calculate the gravitational potential energy associated with the position of the driver. Assume the zero level is at the surface of the pool.

When 1.98 g of NaOH (molar mass = 40 g/mole) are added to 75.0 mL of a 0.350 M HCl solution in a coffee-cup calorimeter, the temperature changes from 21.7°C to 25.8°C. If the resulting solution has a mass of 78.

Magnesium carbonate dissociates to magnesium oxide and carbon dioxide at elevated temperatures. MgCO3 (s) MgO (s) + CO2 (g) A reaction vessel contains these compounds in equilibrium at 300°C.

Sodium an alkali metal and chlorine a halogen are both in period 3 of the periodic table which element has a higher ionization energy

Which of these is a pure substance: sodium metal, solid sodium chloride, sodium chloride dissolved in water?

What is the concentration of hydronium in each of the following cases: [OH-] = 10-12 M? [OH-] = 10-2 M?

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