State of matter and reaction mechanisms

Symbols that represent the state of matter are often added to chemical equations. These symbols give us more information about how the reaction is carried out. The state of matter is important because gases tend to react faster than solids. The particles in a gas are already moving around each other and can find other reactants very easily. Solid particles do not move very quickly and only react at their surface. This makes solid-solid reactions slow. Read the text aloud

As shown in the table, the symbol (s) after a chemical formula means the substance is a solid. A gas is symbolized by (g) and liquids by (l). The equation, 2H₂(g) + O₂(g) → 2H₂O(l) tells us, two moles of hydrogen gas and one mole of oxygen gas react to form two moles of liquid water. Notice how numbers in front of compounds are translated as the number of moles. When a coefficient is not present, assume there is one mole.

Chemical equations can indicate the reaction mechanisms by notations over the arrow. The diagram shows notations for catalysts and heat. An element symbol, such as Pt for platinum, indicates that a platinum catalyst is needed. Heat is sometimes indicated by the capital Greek letter Delta, Δ. Read the text aloud

The symbol (aq) stands for aqueous (aq). This means dissolved in water. Do no confuse aqueous with liquid. Aqueous iron, Fe²⁺(aq) is a rusty water mixture but liquid iron, Fe(l) is molten iron at 1,538 °C or 2,800 °F. In this case, the difference could be deadly! Read the text aloud

Many reactions take place in solution because particles in solution are mobile and can contact each other to react. A good example is the reaction between salt, NaCl, and barium nitrate, Ba(NO₃)₂. These are both ionic substances and dissolve into separate ions. NaCl dissociates into sodium ions, Na⁺, and chloride ions, Cl⁻. Barium nitrate dissociates into Ba²⁺ ions and NO₃⁻ ions. For the reaction, dissolved NaCl reacts with dissolved barium nitrate, Ba(NO₃)₂. Read the text aloud

Two aqueous solutions react to produce a solid.

The symbol (s) beside barium chloride, BaCl₂, means that the BaCl₂ is a solid product - not a solution. This means that it is insoluble and precipitates, or falls out of the solution. The reaction tells us the other product, sodium nitrate, NaNO₃(aq) stays in solution. The sodium and nitrate ions are soluble throughout the reaction. Read the text aloud

Translate the following balanced equation into words.
Na₂S(aq) + 2HCl(aq) → H₂S(g) + 2NaCl(aq)
Show


		194