Assignment:
Basic concepts of Chemistry
Q .1 Define the following
Atomic mass, Gram atomic
mass, Law of multiple proportion, Limiting reagent, Empirical formula,
Molecular formula.
Q.2 Carbon is found to
form two oxides, which contain 42.9% and 27.3% of carbon respectively. Show
that these figures illustrate the law of multiple proportions.
Q.3 How many atoms and
molecules of sulphur are present in 64.0 of (S8)?
Q.4 Calculate the mass of
Na2CO3 which will have the same number of molecules as
contained in 12.3 g of MgSO4.7H2O.
Q.5 Commercially
available concentrated hydrochloric acid contains 38% HCl by mass.
(a) What is the molarity
of this solution? The density is 1.19g/cm-3.
(b) What volume of
concentrated hydrochloric acid is required to make 1.0 L of 0.10 M HCl?
Q.6 Calculate the
molarities and normalities of the solutions obtained on mixing
(i) 100 mL of 0.2 M H2SO4
with 50 mL of 0.1M HCl
(ii) 100 mL of 0.2 N H2SO4
with 50 mL of 0.1M HCl
(iii) 100 mL of 0.1 M H2SO4
with 50 mL of 0.1M NaOH
(iv) 50 mL of 0.1 N H2SO4
with 100 mL of 0.1NaOH.
Q.7 A crystalline salt on
being rendered anhydrous loses 45.6% of its weight. The percentage composition
of the anhydrous salt is: Al = 10.50%, K= 15.1%, S = 24.96% and O = 49.92%
Find the simplest formula
of the anhydrous and crystalline salt.
Q.8 1.0 g of a mixture of
carbonates of calcium and magnesium gave 240 cm3 of CO2
at STP. Calculate the percentage composition of the mixture.
Q.9 A gas mixture of 3.0
litres of propane and butane on complete combustion at STP produced 10 L of CO2.
Find out the composition of the gas mixture.
Q.10 1.5 g of chalk were
treated with 10ml of 4N-HCl.The chalk
was dissolved and the solution made to 100mL.25 mL of this solution required
18.75 mL of 0.2N- NaOH solution for complete neutralisation. Calculate the
percentage of pure CaCO3 in the sample of chalk?
CHEMISTRY Stoichiometry Assignment
Name: --------------------------------------------------------
1. Consider this balanced
chemical equation: 2 NH3 (g) + SO3 (g) + H2O (l)
-> (NH4)2SO4 (aq)
Using proper chemical names for each species,
write a sentence to show how this equation could be read in terms of moles.
2. Carbon monoxide gas reacts with oxygen gas
to produce carbon dioxide gas.
(a) Write a balanced chemical equation for the
reaction.
(b) How many moles of
carbon dioxide gas should be produced when 4.25 moles of carbon monoxide gas
react?
(c) How many moles of
carbon monoxide gas are required to react with 5.8 moles of oxygen gas?
3. Heat is used to
decompose potassium chlorate into potassium chloride and oxygen gas.
2 KClO3(s)à
2 KCl(s) + 3O2 (g) Calculate the number of moles of potassium chloride that
should be produced from the complete decomposition of 51.2 g of potassium
chlorate.
4. This unbalanced equation represents the
complete combustion of propane.
__ C3H8 (g) + __ O2 (g)
__ CO2(g) + __ H2O(g)
(a)
Balance the equation by providing the
missing coefficients.
(b) Calculate the mass of water that should be
produced when 56.06 g of propane is reacted with excess oxygen.
5. Cream of tartar (KHC4H4O6)
and baking soda (NaHCO3) react to produce the carbon dioxide gas
that makes cakes and muffins "rise". KHC4H4O6(aq)
+ NaHCO3(aq)à KNaC4H4O6(aq)
+ CO2(g) + H2O(l) If a baker uses 9.79 g of cream of tartar
and 4.22 g of baking soda in a recipe for buns, which species is in excess and
which is limiting. Justify your answer.
6. Consider this equation for the production
of copper:
2 Al(s) + 3 CuSO4 (aq)à
3 Cu(s) + Al2 (SO4)3(aq)
(a) Calculate the theoretical yield of copper
that should be produced if 70.94 g of aluminium is reacted with excess copper (II)
sulphate?
(b) If the actual yield
of copper was 239.4 g, calculate the percent yield for this reaction.
(c) Give 2 possible reasons why the actual
yield is different than the theoretical yield.
7. Aqueous solutions of calcium
nitrate and sodium phosphate react to produce a precipitate.
__ Ca(NO3)2( ) + __ Na3PO4(
) à
__ Ca3(PO4)2( ) + __ NaNO3( )
(a) Complete the equation
for the reaction by providing coefficients and state of matter subscripts.
(b) Calculate the mass of precipitate that
should be produced if 72.05 g of dissolved calcium nitrate reacts with 48.88 g
sodium phosphate.
(c) Calculate the mass of the limiting reagent
that remains after the reaction is complete.
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