Chemical Reactions

Synthesis reactions

A reaction where two or more elements combine to form a single element (A+B→AB)

decomposition reaction

a reaction where one reactant breaks up into multiple products (AB→A+B)

precipitation reaction

a reaction involving the mixing of two salt solutions to produce an insoluble solid called a precipitate (Cu(NO₃)₂(aq) + 2KOH(aq) → Cu(OH)2(s) + 2KNO3(aq))

salt solubility and state symbols

Salts that are soluble are aqueous (aq); those that are insoluble are solids (s). There are exceptions, which the table will show

reaction rate formula

reaction rate (s^-1) = quantity of product formed/used up (1) / time (s)

list factors affecting reaction rate

temperature, catalysts, concentration, pressure, surface area, and agitation

how does concentration effect reaction rate?

It affects collision frequency because the higher the concentration, the greater the number of reactant particles and the higher the collision frequency.

how does pressure effect reaction rate?

It affects collision frequency because the higher the pressure, the greater the number of atoms in a smaller space and therefore a higher rate of collisions.

how does surface area effect reaction rate?

Surface area affects the collision frequency. This is because the higher the surface area, the more atoms are ‘available’ to react and therefore a higher rate of collisions.

how does temperature effect reaction rate?

Temperature affects collision frequency and successful collisions. This is because the higher the temperature, the greater the kinetic energy particles have, which means they are moving more quickly and are therefore colliding at a faster rate.

how does agitation effect reaction rate?

By stirring the reactants, they are being ‘moved around' and therefore are more likely to collide, so therefore allow for a higher collision frequency.

types of acid reactions and their formulas

acid + base → neutralised + water

metal + acid → salt + hydrogen

acid + hydrogen carbonate → salt + water + hydrogen

acid + metal carbonate → salt + water + carbon dioxide

What is an acid? What ions do they produce? Do they have high or low pH values?

An acid makes hydrogen ions, any substance with a pH level of 6 and below is an acid. the lower the pH, the more acidic the substance

what is a base? what ions do they produce? what level of pH do they have?

Bases/alkalines make hydroxide ions and have a pH level of 8 and above. The more hydroxide ions in a substance, the more alkaline it is.

what salts are produced when acids react with metal compounds? name the salt and its chemical formula

Hydrochloric acid (HCl) makes chloride, nitric acid (HNO₃) makes nitrate, sulfuric acid (H₂SO₄) makes sufate, phosphoric acid (H₃PO₄) makes phosphate, and ethanoic acid (CH₃COOH) makes ethanoate.

What is the chemical equation for this word equation

Magnesium + oxygen → magnesium oxide

Include state symbols and balance

2Mg + O2 → Mg2O2

explain how precipitation occurs in chemical reactions

it occurs when two dissolved ionic solutions mix and form an insoluble solid that seperates from the liquid

how are salts formed in metal reactions?

It happens when the metal replaces the hydrogen atoms in the acid or when it reacts directly with a non-metal

Explain how chemical reactions occur due to the collison theory

when reactancts collide with each other with enough energy and the correct alignment to break old bonds and form new ones.

Define ‘activation energy’

Activation energy is the minimum amount of energy required to break chemical bonds in the reactants so they can form new ones and make the products.

Explain how catalysts effect the rate of a reaction

Catalysts decrease the amount of timeit takes for a reaction to happen without affecting how the reaction turns out. So, without a catalyst, the reaction would be as shown in blue, but with a catalyst, the reaction is as shown in red

Solve this question: Propane, C₃H₈, is a component of liquid petroleum gas (LPG). Calculate the number of propane molecules in a bottle containing 510 g of propane.

n = m / M → 510 / (12.01 × 3) + (1.008 × 8) = 510 / 44.09

n = 11.57 propane molecules

What equation would you use for this question? Calculate the molar mass of ammonium sulfate (NH₄)₂PO₄

The molar mass equation:

Molar mass (M) = mass (m) / # of moles (n)

What equation would you use for this question? How many molecules are in 0.400 moles of dinitrogen pentoxide?

The mole equation:

Number of particles (N) = # of moles (n) * Avogadro's constant (NA)