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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

    Therefore

    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

    Therefore,

    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

wat happens to current if resistors are in parallel connection
Mosima Reply
more current flows from the source that would flow for any of them individually,so the total total resistance is lower
Theoo
what are the isotopes
Tlotlisang Reply
are different types of the same elemant but with different mass or atomic no.
Ayanda
i sotopes are different type of element with same atomic number but different mass number
Tareskay
yes i forgot some details😁
Ayanda
next quetion plz
Tareskay
why don't we insert the negative sign for 5 × 10 - 9 when substituting
Mpho Reply
Why does an enclosed gas exert pressure on the walls of a container
Palesa Reply
State the gay lussacs law
Anna Reply
what is the coefficient of Na in order to balanced the equation?_Na + MgCl2=2NaCl+Mg?
Arcel Reply
2
Okuhle
2
Tlotlisang
2
Praise
2
Anna
2
Anelehr
2
Liyema
the combining power of an element, especially as measured by the number of hydrogen atoms it can displace or combine with.
Dealon Reply
Thanks
REJOYCE
download periodic table from play Store...it will explain everything to u
Dealon
what are orbitals
Sphe Reply
examples of atoms whose Valence energy levels are not full and more to bond and become more stable
Sphe
What is a valency
REJOYCE
what is vacuum
Njabulo Reply
Vacuum, space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal).
Khayalethu
evidence of reaction
Jason Reply
what is the variance if h²4h=5
Kabelo Reply
it's part of chemistry....u have to understand the difference between between hydrogen bonds and the strengthness
Pride Reply
I know the difference between hydrogen bonds and strengthness
Deeco
the definition and the applications
Pride Reply
when a net force is applied on an object of mass ,it will accelerate in the direction of the net force . Acceleration is directly proportional to the net force and inversely proportional to the of an object
Pride
so what about intermolecular force
Deeco
what kind of help u want
Pride Reply
about neuton's second law
Deeco
I'm going to work with you guys
Pride Reply
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Bandile
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Remmington

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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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