When energy is added or removed, is it a physical change, a chemical change, or both?

When small pieces of manganese oxide were added to a solution of hydrogen peroxide, water and oxygen were produced. Manganese oxide was not used up in the reaction.

The reaction N2 + 3 H2 → 2 NH3 is used to produce ammonia. When 450. g of hydrogen was reacted with nitrogen, 1575 g of ammonia were actually produced. What is the percent yield of this reaction? a. 20,7% b. 41,5% c. 62,1% d. 30,8% e.

The model of the atom where the central core contains protons and neutrons surrounded by a cloud of electrons is best described as A) The Bohr model of the atom. B) The modern model of the atom. C) The plum pudding model of the atom.

Select the correct answer. Which of the following tests might confuse blood with leather? A. Takayama OB. Kastle-Meyer C. Teichmann D. LCV

A hydrocarbon contains by mass 82.7% carbon and 17.3% hydrogen. whats the molecular formula?

What type of star has an absolute brightness of 1 and a surface temperature around 7,500 °C?

Explain the difference between two types of elements with respect to the atoms

The ro - group is the nucleophile. think about which group in the alkyl halide (iodoethane) is the leaving group. keep in mind that the leaving group may be one atom or a group of atoms.

An organic compound is classified as aromatic if it cyclic and has a fragrant odor true or false

Which subatomic particles differ in number for two isotopes of the same element, and which subatomic particles will stay consistent between two isotopes of the same element? Explain how you know.