7th model of exam of Physics and Chemistry. 4th ESO.
Name:
Date:
1. Write the following chemical equations and balance them:
a) Ammonium chloride (NH4Cl) and sodium hydroxide react and we obtain ammonia, sodium
chloride and water.
b) Hydrogen fluoride and calcium hydroxide react and we obtain calcium fluoride and water.
c) Iron (II) chloride reacts with barium and we obtain barium chloride and iron.
d) Sodium hydrogencarbonate (NaHCO3) is transformed into sodium carbonate, carbon dioxide and
water.
e) When potassium iodide and lead (II) nitrate react we obtain lead (II) iodide and potassium nitrate.
f) Iodine and hydrogen react and we obtain hydrogen iodide.
(1.5 points)
2. Fill in the following chart relating the mass, moles, molecules and atoms of different substances. It is
obligatory to indicate the process followed to obtain the results:
Substance
Molar mass
Mass
Moles
Number of
Number of
(g/mole)
(g)
molecules
hydrogen atoms
HCl
100
NH3
5
CH4
5 · 1024
H2O
3.6 · 1024
Atomic masses: H=1 u; Cl=35.5 u; N=14 u; C=12 u, O=16 u.
(2 points)
3. We have a container of 12000 cL which contains nitrogen. The pressure of this container is 3.5 atm and
the temperature is 18 ºC.
a) Calculate the number of moles of nitrogen that we have. (0.5 points)
b) Calculate the density of this gas. (0.5 points)
c) Calculate the number of molecules of nitrogen that we have. (0.25 points)
d) Calculate the number of atoms of nitrogen that we have. (0.25 points)
Data: The atomic mass of N is 14 u.
4. Iron (III) oxide reacts with hydrogen and produces iron and water:
Fe2O3 (s)
+
H2 (g) →
Fe (s) +
H2O
a) Balance the chemical equation. (0.25 points)
b) Calculate how many grams of iron can be made from 16.5 g of Fe2O3 when it reacts with enough
hydrogen. (0.75 points)
c) Calculate how many moles and molecules of water will be produced from the 16.5 g of Fe 2O3.
(0.75 points)
d) Calculate how many litres of hydrogen are needed so that the 16.5 g of Fe2O3 react completely,
when the hydrogen is measured at 790 mm Hg and with a temperature of 25 ºC. (0.75 points)
Atomic masses: H=1 u; O=16 u; Fe=56 u.
5. In the combustion of butane, C4H10, it reacts with oxygen to produce carbon dioxide and water.
C4H10 (g) + O2 (g) → CO2 (g) + H2O (g)
a) Balance the chemical equation. (0.25 points)
b) How many grams of butane have reacted if we have obtained 2.46 g of water? (0.75 points)
c) What is the volume of O2 in normal conditions (0º C and 1 atm) that has reacted? (0.75 points)
d) How many litres of CO2 have been released in normal conditions? (0.75 points)
Atomic masses: C=12 u, O=16 u, H=1 u.
7th model of exam of Physics and Chemistry. 4th ESO.
Name:
Date:
1. Write the following chemical equations and balance them:
a) Ammonium chloride (NH4Cl) and sodium hydroxide react and we obtain ammonia, sodium
chloride and water.
NH4Cl + NaOH → NH3 + NaCl + H2O
b) Hydrogen fluoride and calcium hydroxide react and we obtain calcium fluoride and water.
2HF + Ca(OH)2 → CaF2 + 2H2O
c) Iron (II) chloride reacts with barium and we obtain barium chloride and iron.
FeCl2 + Ba → BaCl2 + Fe
d) Sodium hydrogencarbonate (NaHCO3) is transformed into sodium carbonate, carbon dioxide and
water.
2NaHCO3 → Na2CO3 + CO2 + H2O
e) When potassium iodide and lead (II) nitrate react we obtain lead (II) iodide and potassium nitrate.
2KI + Pb(NO3)2 → PbI2 + 2KNO3
f) Iodine and hydrogen react and we obtain hydrogen iodide.
I2 + H2 → 2HI
(1.5 points)
2. Fill in the following chart relating the mass, moles, molecules and atoms of different substances. It is
obligatory to indicate the process followed to obtain the results:
Substance
Molar mass
Mass
Moles
Number of
Number of
(g/mole)
(g)
molecules
hydrogen atoms
36.5
2.74
1.65∙1024
1.65∙1024
HCl
100
24
17
85
3.011∙10
9.033∙1024
NH3
5
24
16
133 g
8.3
2∙1025
CH4
5 · 10
24
18
53.8
2.99
1.8∙10
H2O
3.6 · 1024
Atomic masses: H=1 u; Cl=35.5 u; N=14 u; C=12 u, O=16 u.
(2 points)
HCl: MM=1+35.5=36.5 g/mole
NH3: MM=14+1∙3=17 g/mole
CH4: MM=12+1∙4=16 g/mole
H2O: MM=1∙2+16=18 g/mole
3. We have a container of 12000 cL which contains nitrogen. The pressure of this container is 3.5 atm and
the temperature is 18 ºC.
a) Calculate the number of moles of nitrogen that we have. (0.5 points)
T=18 ºC=291 K
b) Calculate the density of this gas. (0.5 points)
MM(N2)=14∙2=28 g/mole
c) Calculate the number of molecules of nitrogen that we have. (0.25 points)
d) Calculate the number of atoms of nitrogen that we have. (0.25 points)
Data: The atomic mass of N is 14 u.
4. Iron (III) oxide reacts with hydrogen and produces iron and water:
Fe2O3 (s)
+
H2 (g) →
Fe (s) +
H2O
2 Fe (s) +
3 H2O
a) Balance the chemical equation. (0.25 points)
Fe2O3 (s)
+
3 H2 (g) →
b) Calculate how many grams of iron can be made from 16.5 g of Fe2O3 when it reacts with enough
hydrogen. (0.75 points)
MM(Fe2O3)=56∙2+16∙3=160 g/mole
c) Calculate how many moles and molecules of water will be produced from the 16.5 g of Fe 2O3.
(0.75 points)
d) Calculate how many litres of hydrogen are needed so that the 16.5 g of Fe 2O3 react completely,
when the hydrogen is measured at 790 mm Hg and with a temperature of 25 ºC. (0.75 points)
T=25ºC=298 K
Atomic masses: H=1 u; O=16 u; Fe=56 u.
5. In the combustion of butane, C4H10, it reacts with oxygen to produce carbon dioxide and water.
C4H10 (g) + O2 (g) → CO2 (g) + H2O (g)
a) Balance the chemical equation. (0.25 points)
C4H10 +
O2 → 4CO2 + 5H2O
b) How many grams of butane have reacted if we have obtained 2.46 g of water? (0.75 points)
MM(H2O)=1∙2+16=18 g/mole
MM(C4H10)=12∙4+1∙10=58 g/mole
c) What is the volume of O2 in normal conditions (0º C and 1 atm) that has reacted? (0.75 points)
d) How many litres of CO2 have been released in normal conditions? (0.75 points)
Atomic masses: C=12 u, O=16 u, H=1 u.