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When you are busy with these calculations, you will need to remember the following:

1dm 3 = 1 litre = 1000ml = 1000cm 3 , therefore dividing cm 3 by 1000 will give you an answer in dm 3 .

Some other terms and equations which will be useful to remember are shown below:

  • Molarity is a term used to describe the concentration of a solution, and is measured in mol.dm - 3 . The symbol for molarity is M. Refer to chapter [link] for more information on molarity.
  • Moles = molarity (mol.dm - 3 ) x volume (dm 3 )
  • Molarity (mol.dm - 3 ) = m o l e s v o l u m e

Given the equation:

NaOH + HCl NaCl + H 2 O

25cm 3 of a sodium hydroxide solution was pipetted into a conical flask and titrated with 0.2M hydrochloric acid. Using a suitable indicator, it was found that 15cm 3 of acid was needed to neutralise the alkali. Calculate the molarity of the sodium hydroxide.

  1. NaOH: V = 25 cm 3

    HCl: V = 15 cm 3 ; C = 0.2 M

    The equation is already balanced.

  2. M = n V

    Therefore, n(HCl) = M × V (make sure that all the units are correct!)

    M = 0.2mol.dm - 3

    V = 15cm 3 = 0.015dm 3


    n ( H C l ) = 0 . 2 × 0 . 015 = 0 . 003

    There are 0.003 moles of HCl that react

  3. Look at the equation for the reaction. For every mole of HCl there is one mole of NaOH that is involved in the reaction. Therefore, if 0.003 moles of HCl react, we can conclude that the same quantity of NaOH is needed for the reaction. The number of moles of NaOH in the reaction is 0.003.

  4. First convert the volume into dm 3 . V = 0.025 dm 3 . Then continue with the calculation.

    M = n V = 0 . 003 0 . 025 = 0 . 12

    The molarity of the NaOH solution is 0.12 mol.dm 3 or 0.12 M

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4.9 g of sulfuric acid is dissolved in water and the final solution has a volume of 220 cm 3 . Using titration, it was found that 20 cm 3 of this solution was able to completely neutralise 10 cm 3 of a sodium hydroxide solution. Calculate the concentration of the sodium hydroxide in mol.dm - 3 .

  1. H 2 SO 4 + 2 NaOH Na 2 SO 4 + 2 H 2 O

  2. M = n/V

    V = 220 cm 3 = 0.22 dm 3

    n = m M = 4 . 9 g 98 g . m o l - 1 = 0 . 05 m o l s


    M = 0 . 05 0 . 22 = 0 . 23 m o l . d m - 3
  3. Remember that only 20 cm 3 of the sulfuric acid solution is used.

    M = n/V, therefore n = M × V

    n = 0 . 23 × 0 . 02 = 0 . 0046 m o l
  4. According to the balanced chemical equation, the mole ratio of H 2 SO 4 to NaOH is 1:2. Therefore, the number of moles of NaOH that are neutralised is 0.0046 × 2 = 0.0092 mols.

  5. M = n V = 0 . 0092 0 . 01 = 0 . 92 M
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Acid-carbonate reactions

Demonstration : the reaction of acids with carbonates

Apparatus and materials:

Small amounts of sodium carbonate and calcium carbonate (both in powder form); hydrochloric acid and sulfuric acid; retort stand; two test tubes; two rubber stoppers for the test tubes; a delivery tube; lime water. The demonstration should be set up as shown below.

Questions & Answers

examples of soluble substances
Vuyani Reply
The most obvious example of it.. it salt and water where by salt is a solute because it dissolve in water (solvent)... Sugar and rice are example of insoluble because they do not dissolve
a 400 gram package lying on a horizontal surface is aytached to a horizontal string which passes over a smooth pulley.when a mass of 200gram is attached to the other end of the string , the package is on the point of moving . calculate the weight of the package
Luyanda Reply
Assuming zero acceleration then the weight is w= mg which 0.4x9.8 = 3.92N. If you looking for nett F and acceleration in the system then that requires horizontal force and vertical force downwards subtracting upward force. There's no frictional force.
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I've run out of space but begin keeping your own dictionary on physical science. The same would apply to sound, waves, force, acceleration, motion, etc
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What Is A Vector?
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A vector is a force with both magnitude and direction
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reduction is the gain of electrons of an atom ; compound or molecule. reduction is also the decrease of the oxidation number of an atom ; compound / molecule.
state Newton's second law of motion
when resultant or net force act on an object an object will accelerate at the direction of the force at an acceleration directly proportional and inversely proportional to the mass
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In Physics, monochromatic describes light that has the same wavelength so it's one colour
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Reaction in which there is transfer of electrons between elements
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Source:  OpenStax, Siyavula textbooks: grade 11 physical science. OpenStax CNX. Jul 29, 2011 Download for free at http://cnx.org/content/col11241/1.2
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