Molar+Concentrations+and+Making+up+Solutions

__molar concentration and make up solutions __
=** P urpose:   **= According to the concentration of a solution to find out how much of a particular substance exists in a given volume of the solution.( theoretically  +laboratorial)

**Definitions:**
1. The __ **Concentration** __ of the solution is the the measure of how much of amount of [|substance] there is dissolved in a given volume of the solution. 2. A __ **Concentrated** __ solution has a relatively high concentration.(there is a large amount of substance dissolved in the solution) 3. a __ **Dilute** __ solution has a relatively low concentration 4. In solutions, the __ **molar concentration (molarity)** __ of a substance is the number of moles of the substance contained in __ 1L of solution. __ 5.**Meniscus**:The meniscus is the curve seen at the top of a liquid in response to its container. **Concentrated vs. Dilute** Usually, Concentrated solutions are saturated solution Dilute solutions can be formed when put lots of solvent into concentrated solution As usual, concentrated solution has high concentration; however, dilute solution has a low concentration

__calculation method__
= 1.Formula: = Molar concentration=molarity(M)=mole of species(mol)/total volume(L)

Also known as: **__ 2. c=n/V __ (c=molar concentration, （mol/L）) ** // EXAMPLA 1 .: If 5.0 L of solution contain 2.0 mol of NaCl, what is the molarity of the NaCl? //** Molar concentration=2.0 mol/ 5.0 L= 0.4 mol/ L(M)
 * n=number of moles **
 * v=volume(L) **
 * *“M”is the unit symbol of mol/l **
 * *when you write or read the unit symbol “M”, plese written or read as “molar” **
 * *“molar concentration of… ”= **** … **
 * Examples:

// hint: c=n/V, so we need to figure out __n(moles)__ and __V(volume) in order to get c(molarity)__ // // moles of Nacl= 6.92g*1mol/58.5g =0.1183 mol //
 * //  EXAMPLE 2: In a solution what is the NaCl containing 6.92g of Nacl in 500.0ml of lolution?   //**
 * // NaCl //****// =c=n/v=0.1183 mol/0.500L=0.237M //**

= **1.** =

=** 2. **Density=mass/volume = = ** 3. the moles of R produce equals the moles of R.nH2O ** = =

Laboratorial way to make up solutions
volumetric flasks: are used to obtain accurate volumes of solutions. There are different volumes: 10ml, 50ml.100ml,250ml,1000ml,2000ml,etc 1.Add the Required amount of chemical to a flask having an appropriate volume. 2.Then add distilled water to about one-half to two-thirds full of flask. 3.Shake it until the chemical has completely dissolved. 4.Then add distilled water to until the bottom of the meniscus just touches the etched line of flask’s neck. 5.At last, you can use dropper to make sure the accuracy. 6.Re-cap the flask and shake thoroughly until no wavy lines can be seen in the solution
 * Equipment: **
 * steps for making up an aqueous solution: **

= How to Read a Meniscus = Reference: Textbook [] http://google.com http://www.google.com.hk/imglanding?q=volumetric%20flasks&imgurl [|http://www.google.com.hk/imglanding?q=volumetric%] [|http://www.google.com.hk/imglanding?]