Advice 1: How to calculate the titer

Very often in chemical analysis is the mass concentration is used , the titer of the solution that shows the contents of any substance in each milliliter of solution. To record the titerand adopted the symbol in the form of a capital Latin letter t. A unit of measure g/ml .
How to calculate the titer
You will need
  • paper;
  • - handle;
  • calculator.
To find the captionand solute (a simple caption) use the formula:T = m/V,where T is the titer; m – mass of the substance dissolved in the liquid, V is the volume of solution in milliliters or cubic centimeters.
In addition, the titer you will be able to calculate at the designated substance. This value is also called the conditional titerohms. This will require a formula: T (a/b) = mb/ Va,where T (a/b) is the titer of the solution of the substance a in substance b; mb is the mass of substance b(in grams) that interacts with the solution; Va is the volume of solution of the substance a (in milliliters).
For example, you need to find the titer of the solution of phosphoric acid weight 18 g, obtained by dissolving Н3РО4 in 282 ml of water. The density of the solution is equal to 1,031 g/ml. first, find the mass of the prepared solution, with 282 ml of water will equal 282 g: 28+282 = 300 (d). Then, calculate its volume: 300/ 1,031 = 291 (ml). Now substitute into the formula and find the caption: 18/291 = 0,0619(g/ml).
In addition to the above described methods, you can also calculate the titer, knowing the equivalent mass and normality (equivalent concentration).T = SN*MEq/1000,where T is the titer, SN – normality, MEq – equivalent mass.
Often you will encounter tasks that need to Express the titer of one substance through another. For example, this condition: the caption isa set of 20 ml hydrochloric acid solution with a titerof om 0,0035 g/ml had spent 25 ml of sodium hydroxide solution. It is necessary to calculate the titer of NaOH by HCl.
First, write the reaction equation: NaOH + HCl = NaCl + H2O. Then calculate the titer of alkali solution by the formula: T (NaOH) =T(HCl)*V(HCl)*M(NaOH) / M(HCl)*V(NaOH). Substituting numerical values, obtain the titer of sodium hydroxide equal 0,0031 g/ml. it Remains to calculate the necessary to solve the problem significance:T (NaOH/HCl) = T(NaOH)* MEq(HCl) / MEq(NaOH) =0,0028 g/ml
Useful advice
In spite of the same unit, never confuse the titer of the solution density. Because the value of the density indicates the mass of one cubic centimeter of the solution, not the mass of solute in it.

Advice 2 : How to find molar concentration

In the school course of chemistry is found for a term such as molar concentration. It is present in chemistry textbooks intended for University students. To know what is molar mass and how to calculate it, you need as pupils and students who want to just successfully pass a chemistry exam, and those who decided to choose this science as their future profession.
How to find molar concentration
In experiments in analytical chemistry are very often carried out the sampling. In each of the analyses, among other parameters, determine the number of taken substances. In most problems of analytical chemistry have to deal with concepts such as the mole, amount of substance, molar mass and concentration. Chemical concentrations expressed in several ways. There are molar mass and volume concentration.Molar concentration is the ratio of the amount of a substance to the volume of the solution. This concept is found in the course of chemistry on 10 and 11 class. It is expressed as a formula:c (X) = n(X) /V, where n (X) is the number of solute X; V - volume of the solution.Most often, the calculation of the molar concentration is made in respect of solutions, because solutions are composed of water and solute concentration to be determined. The unit of molar concentration is mol/L.
Knowing the formula of molar concentration, it is possible to prepare a solution. If we know the molar concentration, to obtain the solution of the following formula is used:Cb =mb/Mb * VpПо this formula calculate the mass mb of the substance, and Vp does not change (Vp =const). Then a substance of a certain mass is slowly mixed with water and get the solution.
In analytical chemistry the solution of tasks on the solutions, the molar concentration and mass fraction of a substance are interrelated with each other. The mass fraction wb of a solute is the ratio of its mass to the mass mb of the solution mp:wb =mb/mp, where mp =mb+H2O (solution consists of water and a solute)Molar concentration is equal to the product of the mass fraction on the density of the solution divided by the molar mass:сb = wb Pp-pa/ Mb
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