#### Related to [[Atomic bonding]] --- ## Writing chemical reactions - The **molecular formula** shows the reactant molecules and the product molecules *(or compounds)* that are formed by the reaction - The **total Ionic formula** shows **all the DISSOCIATED ions present in the solution on both sides of the equation**. Remember though, that this does **not include water and insoluble compounds** which are still written in their normal molecular form since they are not dissociated into ions. - The **net ionic formula** is the same as the total ionic formula **except spectator ions are omitted**. Remember that **water should never be omitted**. >[!tip] >- Spectator ions are ions that are present on both sides of the equation. >- This means that both the **reactant they are in and the product they become are aqueous or dissolved in the solution.** >[!quote] >#### Example of different equations: >![[Pasted image 20230216122311.png|800]] --- ## Precipitation reactions - This is a reaction where mixing two solutions causes a **precipitate or insoluble product** to form which is an ionic solid. - To determine if a precipitate will form and what the chemical formula of that precipitate is we first split up the reactants into their constituent ions. Match ions of each reactant with ions **of the other reactant** to form the products of the reaction which are **IONIC SOLIDS**. - Use the chart below to determine which of the products is insoluble **meaning it contains at least one of the insoluble cations. >[!quote] >![[Pasted image 20230213124917.png|800]] #### Exceptions --- ## Acid-Base *See [[Acids and bases]]* - This is when hydrogen H+ ions are exchanged between species (always an acid and a base) which **forms new molecules**. specifically acid-base reactions create **water and a salt** that can be both soluble or insoluble. >[!quote] >![[Pasted image 20230216120315.png|700]] - Sometimes water can **act as an acid providing the hydrogen ions** to react with a weak base. This specifically happens with KF *(a weak base)* and water which combine to form HF and KOH. #### Neutralization reactions - These are reactions where **an acid and a base react together to form water and a salt** both of which are neutral *in pH*. - As far as I know **all acid base reactions are technically neutralization reactions**. #### Acid base titrations - This is when we have a solution of an acid or a base with an **unknown concentration**. - To find this concentration we titrate *(slowly pour in)* a base or acid *(the opposite of what is in the unknown solution)* of **a known concentration**. - When the indicator *(a chemical we put in beforehand)* changes color we know that the moles of the **titrant is equal to the moles of the acid or base in the solution.** *This is known as the equivalence point.* >[!quote] >#### Example calculation: >![[Pasted image 20230216124030.png|800]] >![[Files/Chemical reactions.png|800]] --- ## Reduction oxidation >##### Reduction: This is when an element *GAINS* electrons >##### Oxidation: This is when an element *LOSES* electrons. - This is when an [[Electrons|electron]] transfers from one species to another, causing a change in the **oxidation state** of **two species**. - The **oxidizer in a redux reaction** is the compound that **accepts the most electrons** from other species, thus being reduced *(this compounds oxidation state will decrease)*. The reducer is the compound that gives away the most electrons *becoming positively charged (increased oxidation state)*. >[!tip] > - The **oxidation state of an element** is the charge that it would have if the compound that it is apart of was broken up into **ions**. The oxidation state of a compound is just the **charge of that compound**. > - Note that the oxidation state of hydrogen is +1 when it is bonded to a non-metal but -1 when bonded with a metal. Oxygen is -1 in peroxides only and -2 in everything else. > - The oxidation state is all about electronegativity, **more electronegative elements will become negative** and **less electronegative elements become positive!** > > ![[Pasted image 20230216124628.png|800]] >[!caution] >- If a compound has a charge like NO3- then make sure to account for it when calculating the oxidation states of the compound's constituent elements. In NO3- the nitrogen only has a 5+ even though the oxygen is 6+ all combined, this is what makes the compound negatively charged. >- If the compound has a **negative charge that means that there is an excess of electrons**. A positive charge means there are too little. #### Acidic solution - If a redox reaction is taking place in an acidic solution you will need to add enough H+ molecules *(sometimes H3O+ which is the same as H+ will be used)* on the **reactant side of the equation** so that all of the oxygen can react to form **water molecules on the product side of the equation** - Then as always check the charges of molecules on each of the species to make sure they are equal. If they are not than you have done something wrong #### Basic solution - The only difference between balancing a redox reaction in an acidic solution vs a basic solution is that **instead of using H+ ions to balance out the equation you have to use OH- ions.** #### Combustion reactions - Combustion reactions are classified as **reduction-oxidation** reactions since they always have a species reacting with oxygen. - In a combustion reaction **water and CO2 are normally produced**. Both are in their gaseous state due to the excess heat the reaction releases *(exothermic).* >[!quote] >![[Pasted image 20230216124351.png|800]] --- ## Single and double replacement reactions - A **single replacement reaction** is one where **one element switches spots with another element**. - A double replacement reaction is **one where two elements both switch spots with each other.** >[!quote] > >#### Example of single and double replacement reactions ></br> > >![[Chemical reactions-1.png|300]] >![[Chemical reactions-2.png|300]] --- ## Equilibrium - The equilibrium of a reaction is the point at which the concentration *or amount* of both the reactants and the products is no longer changing. Or in other words, when the *[[Rate laws|rate]] of the forward reaction is equal to that of the backwards reaction*. - Reaction can happen in **both directions** we call the reaction from reactants to products the **forward reaction** and we call the reaction from products to reactants the **backwards reaction**. >[!quote] >##### Reaction over time graph > >![[Chemical reactions12312.png|800]] >[!important] > - Note that **large equilibrium constants (K) favor the production of the products while a small equilibrium constant favors the reactants**. --- #mainpage