Exam of Physics and Chemistry. 4th ESO B.
Name:
Date:
1. Write the following chemical reactions and balance them:
a) Nitrogen and hydrogen react to form ammonia.
b) Sulphuric acid and aluminium hydroxide react to form aluminium sulphate and water.
c) Ethyne (C2 H2) reacts with oxygen to form carbon dioxide and water.
d) Sodium hydroxide and chlorine react to form sodium chloride, sodium hypochlorite and water.
e) Siver nitrate and zinc chloride react to form silver chloride and zinc nitrate.
f) Hydrogen iodide and sulphuric acid react to form iodine, sulphur dioxide and water.
g) Potassium hydroxide and hydrobromic acid react to form potassium bromide and water.
h) Palladium (II) chloride and nitric acid react to form palladium (II) nitrate and hydrochloric acid.
(2 points)
2. We have 10.7 moles of barium chloride (BaCl2).
a) Calculate the mass of barium chloride that we have. (0.5 points)
b) Calculate the number of “molecules” of barium chloride that we have. (0.5 points)
c) Calculate the number of atoms of barium that we have. (0.25 points)
d) Calculate the number of atoms of chlorine that we have. (0.25 points)
Data: AM(Ba)=137.3 u; AM(Cl)=35.5 u.
3. When calcium carbonate reacts with hydrochloric acid, calcium chloride, carbon dioxide and water are
formed, according to the following chemical reaction:
CaCO3 (s) + HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)
a) Balance the chemical equation. (0.25 points)
b) Calculate the volume of carbon dioxide (CO2), measured in normal conditions (0ºC and 1 atm) that we
will obtain when 50 g of calcium carbonate (CaCO3) are consumed. (0.75 points)
c) Calculate the volume of hydrochloric acid (HCl) that has been necessary to consume all the calcium
carbonate, if the molarity of the solution of hydrochloric acid is 1.5 M. (0.75 points)
Data: AM(Ca)=40 u; AM(C)=12 u; AM(O)=16 u; AM(H)=1 u; AM(Cl)=35.5 u.
4. Ammonium nitrite (NH4NO2) is decomposed when heated and produces nitrogen and water:
NH4NO2 → N2 (g) + H2O
a) Balance the chemical equation. (0.25 points)
b) Calculate the volume of nitrogen (N2) that we obtain -when it is measured at 30ºC and 745 mm Hg- if
25 g of ammonium nitrite are decomposed. (0.75 points)
Data: AM(N)=14 u; AM(H)=1 u; AM(O)=16 u.
5. Sodium sulphate reacts with barium chloride and we obtain sodium chloride and barium sulphate.
Na2SO4 + BaCl2 → NaCl + BaSO4
a) Balance the chemical equation. (0.25 points)
b) If 100 g of Na2SO4 react with enough BaCl2, what is the mass of NaCl that we will obtain? (0.75
points)
c) What is the mass of BaSO4 that we will obtain? (0.75 points)
Data: AM(Na)=23 u; AM(S)=32 u; AM(O)=16 u; AM(Ba)=137.3 u; AM(Cl)=35.5 u.
6. We dissolve 200 g of copper (II) sulphate (CuSO4) in water until the volume of the solution is 1300
mL. Calculate the molarity of this solution. (1 point)
Data: AM(Cu)=63.6 u; AM(S)=32 u; AM(O)=16 u.
7. The formula of acetic acid is C2H4O2. Calculate the molarity of a solution of acetic acid whose
percentage in mass is 99% and whose density is 1.05 g/mL.
Data: AM(C)=12 u; AM(H)=1 u; AM(O)=16 u. (1 point)
Exam of Physics and Chemistry. 4 th ESO B.
Name:
Date:
1. Write the following chemical reactions and balance them:
a) Nitrogen and hydrogen react to form ammonia.
N2 + 3H2 → 2NH3
b) Sulphuric acid and aluminium hydroxide react to form aluminium sulphate and
water.
3H2SO4 + 2Al(OH) 3 → Al2 (SO4)3 + 6H2O
c) Ethyne (C2H 2) reacts with oxygen to form carbon dioxide and water.
C2H2 + O2 → 2CO2 + H2O
d) Sodium hydroxide and chlorine react to form sodium chloride, sodium hypochlorite
and water.
2NaOH + Cl2 → NaCl + NaClO + H2O
e) Siver nitrate and zinc chloride react to form silver chloride and zinc nitrate.
2AgNO3 + ZnCl2 → 2AgCl + Zn(NO3)2
f) Hydrogen iodide and sulphuric acid react to form iodine, sulphur dioxide and water.
2HI + H2SO4 → I2 + SO2 + 2H2O
g) Potassium hydroxide and hydrobromic acid react to form potassium bromide and
water.
KOH + HBr(aq) → KBr + H2O
h) Palladium (II) chloride and nitric acid react to form palladium (II) nitrate and
hydrochloric acid.
PdCl2 + 2HNO3 → Pd(NO3 )2 + 2HCl (aq)
(2 points)
2. We have 10.7 moles of barium chloride (BaCl2).
a) Calculate the mass of barium chloride that we have. (0.5 points)
MM(BaCl2)=137.3 + 35.5∙2=208.3 g/mole
b) Calculate the number of “molecules” of barium chloride that we have. (0.5 points)
c) Calculate the number of atoms of barium that we have. (0.25 points)
d) Calculate the number of atoms of chlorine that we have. (0.25 points)
Data: AM(Ba)=137.3 u; AM(Cl)=35.5 u.
3. When calcium carbonate reacts with hydrochloric acid, calcium chloride, carbon
dioxide and water are formed, according to the following chemical reaction:
CaCO3 (s) + HCl (aq) → CaCl 2 (aq) + CO2 (g) + H2O (l)
a) Balance the chemical equation. (0.25 points)
CaCO3 (s) +2HCl (aq) → CaCl2 (aq) + CO 2 (g) + H2O (l)
b) Calculate the volume of carbon dioxide (CO 2), measured in normal conditions (0ºC
and 1 atm) that we will obtain when 50 g of calcium carbonate (CaCO 3) are consumed.
(0.75 points)
MM(CaCO3)=40+12+16∙3=100 g/mole
c) Calculate the volume of hydrochloric acid (HCl) that has been necessary to consume
all the calcium carbonate, if the molarity of the solution of hydrochloric acid is 1.5 M.
(0.75 points)
Data: AM(Ca)=40 u; AM(C)=12 u; AM(O)=16 u; AM(H)=1 u; AM(Cl)=35.5 u.
4. Ammonium nitrite (NH4NO2) is decomposed when heated and produces nitrogen and
water:
NH4NO2 → N2 (g) + H2 O
a) Balance the chemical equation. (0.25 points)
NH4NO2 → N2 (g) + 2H2O
b) Calculate the volume of nitrogen (N 2) that we obtain -when it is measured at 30ºC
and 745 mm Hg- if 25 g of ammonium nitrite are decomposed. (0.75 points)
Data: AM(N)=14 u; AM(H)=1 u; AM(O)=16 u.
MM(NH4NO2)=14∙2+1∙4+16∙2=64 g/mole
5. Sodium sulphate reacts with barium chloride and we obtain sodium chloride and
barium sulphate.
Na2SO4 + BaCl2 → NaCl + BaSO4
a) Balance the chemical equation. (0.25 points)
Na2SO4 + BaCl2 → 2NaCl + BaSO4
b) If 100 g of Na2 SO4 react with enough BaCl2, what is the mass of NaCl that we will
obtain? (0.75 points)
MM(Na2 SO4)=23∙2+32+16∙4=142 g/mole
MM(NaCl)=23+35.5=58.5 g/mole
c) What is the mass of BaSO4 that we will obtain? (0.75 points)
MM(BaSO4)=137.3+32+16∙4=233.3 g/mole
Data: AM(Na)=23 u; AM(S)=32 u; AM(O)=16 u; AM(Ba)=137.3 u; AM(Cl)=35.5 u.
6. We dissolve 200 g of copper (II) sulphate (CuSO 4) in water until the volume of the
solution is 1300 mL. Calculate the molarity of this solution. (1 point)
Data: AM(Cu)=63.6 u; AM(S)=32 u; AM(O)=16 u.
MM(CuSO4)=63.6+32+16∙4=159.6 g/mole
7. The formula of acetic acid is C2H4O 2. Calculate the molarity of a solution of acetic
acid whose percentage in mass is 99% and whose density is 1.05 g/mL.
Data: AM(C)=12 u; AM(H)=1 u; AM(O)=16 u. (1 point)
If V=1 L=1000 mL→
MM(acetic acid)=12∙2+1∙4+16∙2=60 g/mole