El mol es definido como la cantidad de materia que contiene determinado número de entidades elementales (átomos, moléculas, etc.) equivalente a la cantidad de átomos que hay PASAR DE GRAMOS A MOLES

A. tenemos 250 g de hierro, ¿Cuántas moles de hierro están contenidos en dicha masa?

a.
4,46 Moles

b.
4,87 Moles

c.
3,76 Moles

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

that's what i got you can count the number of atoms