# Moles and molar concentration - Stoichiometry

### Moles and molar concentration

#### Lessons

###### Notes:

###### In this lesson, we will learn:

- To
**apply** our understanding of moles calculations to solutions.
- To
**understand** the difference between molarity, moles, and mass.
- To be able to
**calculate** molarity of chemicals dissolved in solution.
- To be able to
**calculate** amounts of substance from titration problems.

__Notes:__

- You
__cannot use__ the __molar volume of gas__ constant (22.4 L / mol at STP) if your question is about __a solution__ or is not at standard temperature and pressure (STP). It is __only__ used when dealing with __gases at STP__.
- The same goes for RTP molar volume if not at RTP.

- Molarity means concentration, for chemists - it means the
__amount of moles of a chemical per amount of volume__. For example, in a given volume of solution.
__Units of concentration are abbreviated “M”__. It means moles per litre, written mol / L or mol L$^{-1}$ or moles per cubic decimeters, written mol / dm$^3$ or mol dm$^{-3}$.
__Square brackets__, e.g. [HCl] are used to show that the __concentration__ of a chemical is being referred to.

- You can use the
__formula__ $c=\frac{n}{V}$ to find concentration, where $n$ = number of moles and $V$ is volume (in liters, L, or cubic decimeters, written dm$^3$). You can re-arrange for $n = c * V$.
- A titration is an experiment used to
__find out the unknown concentration__ of an acid by reacting it with a base of known concentration, or vice versa (unknown base with known acid). __This lesson covers titration calculations, not the titration method or procedure.__
- When answering molar concentration questions, make sure you convert your units properly – volume is often given in mL but concentration is measured in moles per litre!

__our understanding of moles calculations to solutions.__**apply**__the difference between molarity, moles, and mass.__**understand**__molarity of chemicals dissolved in solution.__**calculate**__amounts of substance from titration problems.__**calculate**__Notes:__

__cannot use__the__molar volume of gas__constant (22.4 L / mol at STP) if your question is about__a solution__or is not at standard temperature and pressure (STP). It is__only__used when dealing with__gases at STP__.- The same goes for RTP molar volume if not at RTP.

__amount of moles of a chemical per amount of volume__. For example, in a given volume of solution.__Units of concentration are abbreviated “M”__. It means moles per litre, written mol / L or mol L$^{-1}$ or moles per cubic decimeters, written mol / dm$^3$ or mol dm$^{-3}$.__Square brackets__, e.g. [HCl] are used to show that the__concentration__of a chemical is being referred to.

__formula__$c=\frac{n}{V}$ to find concentration, where $n$ = number of moles and $V$ is volume (in liters, L, or cubic decimeters, written dm$^3$). You can re-arrange for $n = c * V$.__find out the unknown concentration__of an acid by reacting it with a base of known concentration, or vice versa (unknown base with known acid).__This lesson covers titration calculations, not the titration method or procedure.__-
##### Intro Lesson

__Expanding our moles calculations__ -
##### 1.

**Find the number of moles and concentration of substances used in chemical reactions.** -
##### 2.

**Find the number of moles and use it to find the volume of substances used in chemical reactions.** -
##### 3.

**Find the number of moles and use it to find the molarity of substances used in chemical reactions.** -
##### 4.

**Find the number of moles and use it to find the quantities of substances used in chemical reactions.**

Consider the reaction:

2 Al$_{\;(s)} +$2 NaON$_{\;(aq)} +$2 H$_2$O$_{\;(l)}$→2 NaAlO$_{2\;(aq)} +$3 H$_{2\;(g)}$