Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision
Name: ………………………………………. Date: ……………………………………………………
Write the scientific term
:
1.
Expresses the chemical symbols and formulas of the reactants and products.
The chemical equation
2.
The smallest part of a substance that can be found in a single state. The properties of the substance are evident in it.
The molecule
3.
The smallest building unit of the substance that participated in chemical reactions.
The atom
4.
The mass of one atom.
The atomic mass
5.
The mass of one molecule in grams.
The mole
6.
The sum of atomic mass of the atoms forming that molecule.
The molecular mass
7.
The amount of one of the reactants when it is less than its molar ratio in the balanced chemical equation.
The limiting reactant
8.
The number of atoms, molecules or ions found in one mole of the substance and equals 6.02 ✕ 10 23 (atom, molecule or ion).
Avogadro’s number
9.
The amount of matter that contains Avogadro’s number of molecules.
The mole
10.
The volume of gas involved in the reaction and produced from it both are in a fixed ratios.
Gay – Lussac’s Law
11.
The equal volumes of different gases contain the same number of molecules under the same standard temperature and pressure.
Avogadro’s Law
12.
The number of units from the particle for each 100 units from the overall.
Weight percentage
13.
A formula expressing the simplest ratio of true numbers between the atoms of elements which formed the compound.
The empirical formula
14.
A symbolic formula of the molecule of the element, or molecule or the formula unit.
It expresses the actual type and number of atoms or ions that form this molecule or unit.
Chemical formula http://pisscience.wikispaces.com/

Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision
15.
The amount of a substance which we practically obtain from a reaction
The practical yield
16.
The amount of the calculated substance based on the reaction's equation.
The theoretical yield
Give reason for the following
:
1.
The volume occupied by 26 g of acetylene C
2
H
2
at (STP) is equal to the volume occupied by 2 g of hydrogen at the same conditions.
Because 26 grams of acetylene and 2 grams of hydrogen represent 1 mole and one mole of any substance have the same volume
2.
The difference in the molar mass of phosphorus by the difference in its physical state.
Because when phosphorus is in solid state the molecule consists of 1 atom only, while when it is in vapor state the molecule consists of 4 atoms
3.
One liter of oxygen gas contains the same number of molecules that one liter of chlorine gas contains at STP.
Because according to Avogadro’s Law equal volumes of different gases contains the same number of molecules.
4.
The number of molecules of 9 g of water (H
2
O) is equal to the number of molecules of 39 g aromatic benzene C
6
H
6
.
Because 9 grams of water and 39 grams of aromatic benzene = 0.5 mole and according to
Avogadro’s number one mole of any substance contains the same number of molecules
5.
The chemical equation should be balanced.
Because according to the law of conservation the number of atoms in reactants must equal the number of atoms in the products
6.
When you calculate the gas volume in terms of its molar mass, it should be placed in the standard conditions of pressure and temperature.
Because equal volumes contain the same number of molecules only under standard temperature and pressure
7.
The practical yield is always less than the theoretical yield of the equation.
Some of products evaporate – some of the products clink on the walls of the test tubes or beakers – some products may not be pure enough
8.
The molar mass of the sulfur in the solid state differs from its molar mass in the gaseous state.
Because in solid state the molecule consists of 1 atom only while in gaseous state the molecule consists of 8 atoms
Choose the correct answer
:
1.
Number of water moles found in 36 g of it are (0.5 – 1 – 2 – 2.5) moles.
2.
Number of carbon dioxide molecules found in 128 g of it equals (2 –
6.022 × 10 23 – 3.011× 10 23 – 18.044 × 10 23 ) molecules.
3.
Number of produced sodium ions from dissolving 40 g of NaOH in water equals (2 –
6.022 × 10 23 – 3.011× 10 23 – 18 × 10 23 ) ions. http://pisscience.wikispaces.com/

Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision
4.
The volume of 4 g of hydrogen molecules H
2
in standard conditions (STP) equals (2
– 22.4 –
44.8
– 89.6) liter.
5.
The volumes of producing gasses from the reaction are directly proportional with the participating gas volumes in the reaction (Avogadro’s Law - Avogadro’s number -
Jay-Lussac Law - Law of Mass Reservation).
6.
The number of the empirical formula units of the compound C
2
H
2
O
4
is (1 – 2 – 3 –
4).
7.
The mass of CaO resulted from dissociating 50 g of calcium carbonate CaCO
3 thermally is ( 28
– 82 – 96 – 14) grams.
8.
The number of hydrogen moles needed to produce 11.2 L of water vapor at (STP) is
(22.4 – 44.8 – 0.5
– 68.2) liter.
9.
If the empirical formula of a compound is CH
2
and its molecular mass is 56 , then the molecular formula of such a compound is (C
3
H
6
- C
2
H
4
– C
4
H
8
– C
5
H
10
).
10.
The masses of atomic particles are estimated by the unit of atomic masses (a.m.u) which equals (one atomic mass unit equals ????? in grams) (6.022 × 10 23 – 1.66 ×
10 23 – 1.66 × 10 -23 – 1.66 × 10 -24 ) grams. Calculate in Kg.
11.
The unit used in the international system SI to express the amount of a substance is
(gram – kilogram – mole – unit of atomic masses).
12.
The number of grams of 44.8 L of ammonia gas NH
3
at (STP) equals (2 – 17 – 34 –
0.5) grams.
13.
If an amount of sodium contains 3.01 ✕ 10 23 atoms, then the mass of this amount equals ( 11.5
– 23 – 46 – 0.5) grams.
14.
A chemical equation is to be balanced to satisfy (Avogadro - Reservation of energy -
Reservation of mass - Gay & Lussac).
15.
Half a mole of carbon dioxide CO
2
is (44 – 22 – 88 – 66).
16.
The empirical formula of CH
2
O expresses the molecular formula of (HCHO -
CH
3
COOH - C
6
H
12
O
6
).
17.
When 64 g of oxygen reacts with abundance of hydrogen, then the volume of the water vapor resulted in STP is (22.4 - 44.8 - 11.2 - 89.6
).
Solve the following problems
:
First : Calculate the molecular formula for a compound contains carbon with a ratio 85.7 % and hydrogen with a ratio 14.3 % and its molecular mass is 42.
C H
85.7 14.3
12 1
7.14 14.3
1 2 the empirical formula CH
2
The number of empirical units = molecular mass / empirical mass = 42/14 = 3
The chemical formula C
3
H
6 http://pisscience.wikispaces.com/

Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision
Second :130 g of silver chloride precipitated when a mole of sodium chloride dissolved in water reacted with silver nitrate solution. Calculate the following:
.
The percentage of the actual product
The percentage of the actual yield = (the actual yield \ theoretical yield) * 100
= (130/143.5) *100 = 90.59%
2 The number of sodium ions resulted from this reaction.
AgNO
3
+ NaCl → AgCl + NaNO
3
1 mole of sodium ions is produced then the number of sodium ions = Avogadro’s number
= 6.022 × 10 23
Third : Calculate the number of moles of 144 g of carbon.
1 mole of carbon 12 grams
How many moles 144 grams
How many moles = 144/12 = 12 moles
Fourth : Calculate the mass of 2.4 mole of a limestone CaCO
3
1 mole of CaCO
3
100 grams
2.4 mole how many grams
How many grams = 2.4 × 100 = 240 gram
Sixth : Calculate the volume of 56 g of nitrogen at (STP).
The mass of 1 mole of nitrogen 14 gram
How many moles 56 grams
How many moles = 56/14 = 4 mole
The volume of gas = the number of moles × 22.4
= 4 × 22.4 = 89.6 Liter
Seventh : Calculate the volume of hydrogen and the number of sodium ions resulted from the reaction of 23 g of sodium and an excess amount of water in the standard conditions according to the following equation:
2Na + 2H
2
O → 2NaOH + H
2
4 moles of hydrogen atoms
The volume of gas = the number of moles ×
= 4 × 22.4 = 89.6 liter
Eighth : Calculate the volume of one mole of phosphorus in the gaseous state at (STP), and then calculate the number of the atoms in this volume.
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Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision
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Ninth : 39.4 g of barium sulfate BaSO
4
precipitated when 40 g of barium chloride solution
BaCl
2
reacted with an abundance of potassium sulfate. Calculate the percentage of the practical yield of barium sulphate.
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Tenth : Calculate the ratio of iron present in the raw siderite FeCO
3
.
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……………………………………………………………………………………………… http://pisscience.wikispaces.com/

Port Said International Schools
Better Education for Future Generations Grade: 10
Science Department Unit 2 Revision http://pisscience.wikispaces.com/