Chemical properties

The external electronic configuration of the Zn atom is 3d 10 4s 2. The oxidation state in compounds is +2. The normal redox potential of 0.76 V characterizes Zinc as active metal and an energetic restorer. In air at temperatures up to 100 °C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In air, zinc becomes covered with a thin film ZnO oxide. When heated strongly, it burns to form amphoteric white oxide ZnO.

2Zn + O 2 = 2ZnO

Dry fluorine, chlorine and bromine do not react with Zinc in the cold, but in the presence of water vapor the metal can ignite, forming, for example, ZnCl 2. A heated mixture of zinc powder and sulfur gives zinc sulfide ZnS. Zinc sulfide precipitates when hydrogen sulfide acts on weakly acidic or ammoniacal aqueous solutions of Zn salts. ZnH 2 hydride is obtained by reacting LiAlH 4 with Zn(CH 3) 2 and other zinc compounds; a metal-like substance that decomposes into elements when heated.

Nitride Zn 3 N 2 - black powder, is formed when heated to 600 ° C in a stream of ammonia; stable in air up to 750 °C, water decomposes it. Zinc carbide ZnC 2 was obtained by heating zinc in a stream of acetylene. Strong mineral acids vigorously dissolve zinc, especially when heated, to form the corresponding salts. When interacting with dilute HCl and H 2 SO 4, H 2 is released, and with HNO 3, in addition, NO, NO 2, NH 3. Zinc reacts with concentrated HCl, H 2 SO 4 and HNO 3, releasing H 2, SO 2, NO and NO 2, respectively. Solutions and melts of alkalis oxidize zinc, releasing H2 and forming water-soluble zincites. The intensity of the action of acids and alkalis on zinc depends on the presence of impurities in it. Pure zinc is less reactive towards these reagents due to its high hydrogen overvoltage. In water, Zinc salts hydrolyze when heated, releasing a white precipitate of Zn(OH) 2 hydroxide. Known complex compounds containing Zinc, for example SO 4 and others.

Zinc oxide reacts both with acid solutions:

ZnO + 2HNO 3 = Zn(NO 3) 2 + H 2 O

and with alkalis:

ZnO + 2NaOH (fusion) = Na 2 ZnO 2 + H 2 O

Zinc of ordinary purity reacts actively with acid solutions:

Zn + 2HCl = ZnCl 2 + H2

Zn + H 2 SO 4 = ZnSO 4 + H 2

and alkali solutions:

Zn + 2NaOH + 2H 2 O = Na 2 + H 2

forming hydroxinates. Very pure zinc does not react with solutions of acids and alkalis. The interaction begins when a few drops of copper sulfate solution CuSO 4 are added.

When heated, zinc reacts with non-metals (except hydrogen, carbon and nitrogen). Reacts actively with acids:

Zn + H 2 SO 4 (diluted) = ZnSO 4 + H 2

Zinc is the only element of the group that dissolves in aqueous solutions alkalis with the formation of 2– ions (hydroxycinates):

Zn + 2OH – + 2H 2 O = 2– + H 2

When metallic zinc is dissolved in an ammonia solution, an ammonia complex is formed:

Zn + 4NH 3 H 2 O = (OH) 2 + 2H 2 O + H 2

The external electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The normal redox potential of 0.76 V characterizes zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 °C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In humid air, especially in the presence of CO2, the metal decomposes with the formation of basic zinc bicarbonate, even at ordinary temperatures.

At red-hot temperatures, it can be oxidized by water vapor, releasing hydrogen and carbon dioxide. When heated sufficiently in air, it burns with a bright greenish-blue flame to form zinc oxide with a significant release of energy.

In accordance with the place occupied by zinc in the series of stresses, it readily dissolves in dilute acids with the release of hydrogen. At the same time concentrated acid is reduced to nitrogen oxides, diluted - to ammonia. Dissolution in conc. H3S04 is accompanied by the release of sulfur dioxide, not hydrogen.

A mixture of zinc powder and sulfur reacts explosively when heated.

Zinc does not interact with nitrogen even in vapor, but quite easily at red heat it reacts with ammonia, forming zinc nitride - Zn3Na.

Zinc carbide ZnC, formed by heating zinc in a stream of acetylene, decomposes with water and dilute acids.

When metallic zinc is heated in phosphorus vapor to 440-780°C, phosphides are formed - Zn3Ps and ZnP2.

In the molten state, zinc mixes indefinitely with many metals: Cu, Ag, Au, Cd, Hg, Ca, Mg, Mn, Fe, Co, Ni, Al, Sn.

Zinc forms compounds with many metals, for example: Cu, Ag, Au, Mn, Fe, Co, Ni, Pf, Pd, Rh, Sb, Mg, Ca, Li, Na, K.

Zinc dissolves quite easily in alkalis, as well as aqueous solutions of ammonia and ammonium chloride, especially when heated. The rate of dissolution of zinc not only in alkalis, but also in acids depends on its purity. Very pure zinc dissolves slowly, and to speed up the process it is recommended to introduce a few drops of a highly diluted solution of copper sulfate into the solution (the appearance of galvanic couples).

Interaction with non-metals

When heated strongly in air, it burns with a bright bluish flame to form zinc oxide:

When ignited, it reacts vigorously with sulfur:

Reacts with halogens under normal conditions in the presence of water vapor as a catalyst:

Zn + Cl2 = ZnCl2

When phosphorus vapor acts on zinc, phosphides are formed:

Zn + 2P = ZnP2 or

3Zn + 2P = Zn3P2

Zinc does not interact with hydrogen, nitrogen, boron, silicon, or carbon.

Interaction with water

Reacts with water vapor at red heat to form zinc oxide and hydrogen:

Zn + H2O = ZnO + H2

Interaction with acids

In the electrochemical voltage series of metals, zinc is located before hydrogen and displaces it from non-oxidizing acids:

Zn + 2HCl = ZnCl2 + H2

Zn + H2SO4 = ZnSO4 + H2

Interacts with diluted nitric acid, forming zinc nitrate and ammonium nitrate:

4Zn + 10HNO3 = 4Zn(NO3)2 + NH4NO3 + 3H2O

Reacts with concentrated sulfuric and nitric acids to form zinc salt and acid reduction products:

Zn + 2H2SO4 = ZnSO4 + SO2 + 2H2O

Zn + 4HNO3 = Zn(NO3)2 + 2NO2 + 2H2O

Interaction with alkalis

Reacts with alkali solutions to form hydroxo complexes:

Zn + 2NaOH + 2H2O = Na2 + H2

when fused, it forms zincates:

Zn + 2KOH = K2ZnO2 + H2

Interaction with ammonia

With gaseous ammonia at 550-600°C it forms zinc nitride:

3Zn + 2NH3 = Zn3N2 + 3H2

dissolves in an aqueous solution of ammonia, forming tetraamminium zinc hydroxide:

Zn + 4NH3 + 2H2O = (OH)2 + H2

Interaction with oxides and salts

Zinc displaces metals located in the voltage series to the right of it from solutions of salts and oxides:

Zn + CuSO4 = Cu + ZnSO4

The element zinc (Zn) in the periodic table has serial number 30. It is in the fourth period of the second group. Atomic weight - 65.37. Distribution of electrons over layers 2-8-18-2

The origin of the element's name is unclear, but it seems plausible that it is derived from Zinke (German for "point" or "tooth"), thanks to appearance metal

Zinc is a bluish-white metal that melts at 419 C and turns into steam at 913 C; its density is 7.14 g/cm3. At ordinary temperatures, zinc is quite brittle, but at 100-110 C it bends well and is rolled into sheets. In air, zinc is coated with a thin layer of oxide or basic carbonate, which protects it from further oxidation.

Water has almost no effect on zinc, although it is located in the series of voltages significantly to the left of hydrogen. This is explained by the fact that the hydroxide formed on the surface of zinc when it interacts with water is practically insoluble and prevents the further course of the reaction. In dilute acids, zinc easily dissolves to form the corresponding salts.

In addition, zinc, like beryllium and other metals that form amphoteric hydroxides, dissolves in alkalis. If zinc is heated in air to its boiling point, its vapor ignites and burns with a greenish-white flame, forming zinc oxide

When heated, zinc reacts with non-metals (except hydrogen, carbon and nitrogen). Reacts actively with acids:

Zn + H2SO4 (diluted) = ZnSO4 + H2

Zinc is the only element of the group that dissolves in aqueous solutions of alkalis to form ions (hydroxycinates):

Zn + 2OH + 2H2O = + H2

Physical properties of Zinc. Zinc is a medium-hard metal. When cold it is fragile, but at 100-150 °C it is very plastic and easily rolled into sheets and foil with a thickness of about hundredths of a millimeter. At 250 °C it becomes brittle again. It has no polymorphic modifications. Crystallizes in a hexagonal lattice with parameters a = 2.6594Å, c = 4.9370Å. Atomic radius 1.37Å; ionic Zn2+ -0.83Å. The density of solid Zinc is 7.133 g/cm3 (20 °C), liquid 6.66 g/cm3 (419.5 °C); melting point 419.5 °C; boiling point 906 °C. Temperature coefficient of linear expansion 39.7 10-3 (20-250 °C), thermal conductivity coefficient 110.950 W/(m K) 0.265 cal/cm sec °C (20 °C), electrical resistivity 5.9 10-6 ohm cm (20 °C), specific heat Zinc 25.433 kJ/(kg K.) . Tensile strength 200-250 MN/m2 (2000-2500 kgf/cm2), relative elongation 40-50%, Brinell hardness 400-500 MN/m2 (4000-5000 kgf/cm2). Zinc is diamagnetic, its specific magnetic susceptibility is -0.175·10-6.

Chemical properties of Zinc. The external electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The standard electrode potential of -0.76 V characterizes Zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 °C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In humid air, especially in the presence of CO2, metal destruction occurs even at normal temperatures. When strongly heated in air or oxygen, Zinc burns intensely with a bluish flame, producing white smoke of zinc oxide ZnO. Dry fluorine, chlorine and bromine do not react with Zinc in the cold, but in the presence of water vapor the metal can ignite, forming, for example, ZnCl2. A heated mixture of Zinc powder and sulfur gives Zinc sulfide ZnS. Zinc sulfide precipitates when hydrogen sulfide reacts with weakly acidic or ammoniacal aqueous solutions of Zn salts. ZnH2 hydride is obtained by reacting LiAlH4 with Zn(CH3)2 and other Zinc compounds; a metal-like substance that decomposes into elements when heated. Zn3N2 nitride is a black powder, formed when heated to 600 °C in a stream of ammonia; stable in air up to 750 °C, water decomposes it. Zinc carbide ZnC2 is obtained by heating Zinc in a stream of acetylene. Strong mineral acids vigorously dissolve Zinc, especially when heated, to form the corresponding salts. When interacting with dilute HCl and H2SO4, H2 is released, and with HNO3, in addition, NO, NO2, NH3. Zinc reacts with concentrated HCl, H2SO4 and HNO3, releasing H2, SO2, NO and NO2, respectively. Solutions and melts of alkalis oxidize zinc, releasing H2 and forming water-soluble zincites. The intensity of the action of acids and alkalis on zinc depends on the presence of impurities in it. Pure Zinc is less reactive towards these reagents due to its high hydrogen overvoltage. In water, Zinc salts hydrolyze when heated, releasing a white hydroxide precipitate.

a) interaction of zinc with dilute acids

Zn(OH)2. H2SO4 + Zn = ZnSO4 + H2

Zinc, as an active metal, can form sulfur dioxide, elemental sulfur, and even hydrogen sulfide with concentrated sulfuric acid.

2H2SO4 + Zn = SO2 +ZnSO4 + 2H2O

When zinc reacts with very dilute nitric acid, ammonia is released, which reacts with the excess acid to form ammonium nitrate.

Zinc does not appear in nature as a native metal. Zinc is mined in two ways:

1) pyrometallurgical method

2) hydrometallurgical method from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. Ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and at the same time lead, copper, and sometimes also pyrite concentrates. Zinc concentrates are fired in fluidized bed furnaces, converting zinc sulfide into ZnO oxide; The resulting sulfur dioxide SO2 is used to produce sulfuric acid. There are two routes from ZnO to Zn.

1) According to the pyrometallurgical (distillation) method, which has existed for a long time, the calcined concentrate is subjected to sintering to impart granularity and gas permeability, and then reduced with coal or coke at 1200 - 1300 ° C:

ZnO + C = Zn + CO.

The resulting metal vapors are condensed and poured into molds. At first, reduction was carried out only in retorts made of baked clay, operated manually, later they began to use vertical mechanized retorts made of carborundum, then - shaft and arc electric furnaces; Zinc is obtained from lead-zinc concentrates in blast furnaces. Productivity gradually increased, but zinc contained up to 3% impurities, including valuable cadmium. Distillation zinc is purified by segregation (that is, by settling the liquid metal from iron and part of the lead at 500 °C), achieving a purity of 98.7%. Sometimes used, more complex and expensive purification by rectification gives the metal a purity of 99.995% and allows the recovery of cadmium.

The main method of obtaining zinc is electrolytic (hydrometallurgical). The roasted concentrates are treated with sulfuric acid; the resulting sulfate solution is cleaned of impurities (by precipitating them with zinc dust) and subjected to electrolysis in baths tightly lined inside with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is removed (stripped off) daily and melted in induction furnaces. Typically, the purity of electrolytic zinc is 99.95%, the completeness of its extraction from the concentrate (taking into account waste processing) is 93-94%. Zinc sulfate, Pb, Cu, Cd, Au, Ag are obtained from production waste; sometimes also In, Ga, Ge, Tl.

2) The hydrometallurgical method for processing roasted zinc concentrates consists of dissolving zinc oxide with an aqueous solution of sulfuric acid and subsequent precipitation of zinc by electrolysis. Therefore, the hydrometallurgical method is sometimes called electrolytic. When producing zinc by electrolysis, the zinc concentrate is first subjected to oxidative roasting.

ZnSO4→ Zn 2+ + SO4 2-

2+ (–) cathode Zn, Н2О (+) anode: SO42–, Н2О

Zn + 2e Zn 2H2O – 4e O2 + 4H+

2H2O + 2eH2 + 2HO

Summary equation

ZnSO4 + 2H2O Zn + H2 + O2 + H2SO4.

The resulting cinder is leached with a spent electrolyte containing sulfuric acid. The resulting solution of zinc sulfate is purified from harmful impurities and sent for electrolysis. In this case, zinc is deposited on the cathode, and sulfuric acid is regenerated in the solution, which is returned again for leaching

If the roasting of zinc concentrate precedes leaching, then its purpose is the most complete conversion of zinc sulphide into zinc oxide, soluble in dilute solutions of sulfuric acid.

Leaching of cinder is carried out with a spent electrolyte containing sulfuric acid and obtained by electrolysis of a zinc solution. During the processing process, losses of sulfuric acid are inevitable (both mechanical, occurring due to loss of solution, and chemical, caused by the fact that sulfuric acid is unproductively spent on dissolving impurities). These losses are replenished by obtaining in the cinder a certain amount of zinc sulfate, which easily dissolves in water. For this purpose, it is enough to have about 2-4% sulfate sulfur in the calcined concentrate.

About 70% of the world's zinc production is obtained this way. This is explained by the fact that the electrolytic method, with good mechanization of labor-intensive processes and a high percentage of extraction, produces purer zinc than distillation. In addition, the possibility of complex use of the valuable components of the concentrate is facilitated. To isolate zinc, the ZnS concentrate obtained after enrichment is fired:

2ZnS+3O2→ 2ZnO+2SO2

In general terms:

4Zn + 10HNO3 = 4Zn(NO3)2 + NH4NO3 + 3H2O

Zn + HNO3 = Zn(NO3)2 +NO +H2O

b) Interaction of soluble zinc salts with alkalis:

ZnCl2 +2NaOH= ZnOH2↓+2NaCl

Zn(NO3)2+2KOH = ZnOH2↓ +2KNO3

Located in the second group, side subgroup periodic table Mendeleev and is a transition metal. The serial number of the element is 30, mass is 65.37. Electronic configuration the outer layer of the atom is 4s2. The only and constant is “+2”. Transition metals are characterized by the formation of complex compounds in which they act as a complexing agent with different coordination numbers. This also applies to zinc. There are 5 isotopes that are stable in nature with mass numbers from 64 to 70. Moreover, the 65Zn isotope is radioactive, its half-life is 244 days.

Zinc is a silvery-blue metal that, when exposed to air, quickly becomes coated with a protective oxide film, hiding its shine. When the oxide film is removed, zinc exhibits the properties of metals - radiance and a characteristic bright shine. In nature, zinc is found in many minerals and ores. The most common: cleiophane, zinc blende (sphalerite), wurtzite, marmatite, calamine, smithsonite, willemite, zincite, franklinite.

Smithsonite

As part of mixed ores, zinc meets its constant companions: thallium, germanium, indium, gallium, and cadmium. IN earth's crust contains 0.0076% zinc, and 0.07 mg/l of this metal is contained in sea ​​water in the form of salts. Zinc formula as simple substance- Zn, chemical bond- metal. Zinc has a hexagonal dense crystal lattice.

Physical and chemical properties of zinc

The melting point of zinc is 420 °C. Under normal conditions it is a brittle metal. When heated to 100-150 °C, the malleability and ductility of zinc increases, and it is possible to manufacture wire from the metal and roll foil. The boiling point of zinc is 906 °C. This metal is an excellent conductor. Starting from 200 °C, zinc is easily ground into gray powder and loses its plasticity. The metal has good thermal conductivity and heat capacity. The described physical parameters allow the use of zinc in compounds with other elements. Brass is the most well-known zinc alloy.

Brass wind instruments

Under normal conditions, the surface of zinc is instantly covered with oxide in the form of a dull gray-white coating. It is formed due to the fact that oxygen in the air oxidizes a pure substance. Zinc as a simple substance reacts with chalcogens, halogens, oxygen, alkalis, acids, ammonium (its salts), . Zinc does not interact with nitrogen, hydrogen, boron, carbon and silicon. Chemically pure zinc does not react with solutions of acids and alkalis. - the metal is amphoteric, and in reactions with alkalis it forms complex compounds - hydroxinates. Click to find out what experiments to study the properties of zinc can be done at home.

Reaction of sulfuric acid with zinc and production of hydrogen

The reaction of dilute sulfuric acid with zinc is the main laboratory method for producing hydrogen. For this purpose, pure grained (granulated) zinc or technical zinc in the form of scraps and shavings is used.

If very pure zinc and sulfuric acid are taken, then hydrogen is released slowly, especially at the beginning of the reaction. Therefore, a little copper sulfate solution is sometimes added to the solution that has cooled after dilution. Copper metal deposited on the surface of the zinc accelerates the reaction. The optimal way to dilute an acid to produce hydrogen is to dilute concentrated sulfuric acid with a density of 1.19 with water in a 1:1 ratio.

Reaction of concentrated sulfuric acid with zinc

In concentrated sulfuric acid, the oxidizing agent is not the hydrogen cation, but a stronger oxidizing agent - the sulfate ion. It does not manifest itself as an oxidizing agent in dilute sulfuric acid due to strong hydration and, as a result, low mobility.

How concentrated sulfuric acid will react with zinc depends on temperature and concentration. Reaction equations:

Zn + 2H₂SO₄ = ZnSO₄ + SO₂ + 2H₂O

3Zn + 4H₂SO₄ = 3ZnSO₄ + S + 4H₂O

4Zn + 5H₂SO₄ = 4ZnSO₄ + H₂S + 4H₂O

Concentrated sulfuric acid is a strong oxidizing agent due to the oxidation state of sulfur (S⁺⁶). It interacts even with low-active metals, that is, with metals before and after hydrogen, and, unlike dilute acid, never releases hydrogen during these reactions. In reactions of concentrated sulfuric acid with metals, three products are always formed: salt, water and a sulfur reduction product. Concentrated sulfuric acid is such a strong oxidizing agent that it even oxidizes some non-metals (coal, sulfur, phosphorus).

DEFINITION

Zinc- the thirtieth element of the periodic table. Designation - Zn from the Latin "zincum". Located in the fourth period, group IIB. Refers to metals. The core charge is 30.

The main natural zinc compounds from which it is extracted are the minerals galmei ZnCO 3 and zinc blende ZnS. The total zinc content in the earth's crust is approximately 0.01% (wt).

Zinc is a bluish-silver metal (Fig. 1). At room temperature it is quite fragile, but at 100-150 o C it bends well and is rolled into sheets. When heated above 200 o C, zinc becomes very brittle. When exposed to air, it becomes coated with a thin layer of oxide or basic carbonate, which protects it from further oxidation. Water has almost no effect on zinc.

Rice. 1. Zinc. Appearance.

Atomic and molecular weight of zinc

Relative molecular mass of the substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and relative atomic mass element (A r)- how many times the average mass of atoms chemical element more than 1/12 the mass of a carbon atom.

Since in the free state zinc exists in the form of monatomic Zn molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 65.38.

Zinc isotopes

It is known that in nature chromium can be found in the form of five stable isotopes 64 Zn, 66 Zn, 67 Zn, 68 Zn and 70 Zn. Their mass numbers are 64, 66, 67, 68 and 70, respectively. The nucleus of an atom of the zinc isotope 64 Zn contains thirty protons and thirty-four neutrons, and the remaining isotopes differ from it only in the number of neutrons.

There are artificial unstable isotopes of zinc with mass numbers from 54 to 83, as well as ten isomeric states of nuclei, among which the longest-lived isotope is 65 Zn with a half-life of 243.66 days.

Zinc ions

On the outside energy level The zinc atom has two electrons, which are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 .

As a result chemical interaction zinc gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Zn 0 -2e → Zn 2+ .

Zinc molecule and atom

In the free state, zinc exists in the form of monoatomic Zn molecules. Here are some properties characterizing the zinc atom and molecule:

Zinc alloys

Alloys of zinc with aluminum, copper and magnesium are of wide industrial importance. With copper, zinc forms an important group of alloys - brass. Brasses contain up to 45% zinc. There are simple and special brass. The latter contains other elements, such as iron, aluminum, tin, and silicon.

Examples of problem solving

EXAMPLE 1

Exercise	Technical zinc weighing 0.33 g was treated with a dilute solution of sulfuric acid. The released hydrogen occupies a volume of 112 ml under normal conditions. Calculate the mass fraction of zinc in the industrial metal.
Solution	Let us write the equation for the reaction of zinc with dilute sulfuric acid: Zn + H 2 SO 4 (dilute) = ZnSO 4 + H 2. Let's find the number of moles of hydrogen released during the reaction: n (H 2) = V (H 2) / V m; n (H 2) = 112 × 10 -3 / 22.4 = 0.005 mol. According to the reaction equation n (H 2):n (Zn) = 1:1, i.e. n (H 2) = n (Zn) = 0.005 mol. Then, the mass of pure zinc (without impurities) will be equal to ( molar mass- 65 g/mol): m pure (Zn) = 0.005 × 65 = 0.325 g. Mass fraction zinc in technical metal is calculated as: ω(Zn) = m pure (Zn)/ m tec (Zn) × 100%; ω(Zn) = 0.325/ 0.33 × 100%; ω(Zn) = 98.48%.
Answer	The mass fraction of zinc in the technical metal is 98.48%.

EXAMPLE 2

Exercise	Calculate the mass of zinc that must be dissolved in hydrochloric acid to obtain the hydrogen necessary to reduce 20 g of copper (II) oxide to metal.
Solution	Let us write down the equations of reactions that occur according to the conditions of the problem: Zn + 2HCl = ZnCl 2 + H 2 (1); H 2 + CuO = Cu + H 2 O (2). Let's calculate the amount of copper (II) oxide (molar mass - 80 g/mol): n (CuO) = m (CuO) / M (CuO); n (CuO) = 20 / 80 = 0.25 mol. According to equation (2) n (CuO):n (H 2) = 1:1, i.e. n (CuO) = n (H 2) = 0.25 mol. Then, the number of moles of zinc that reacted with hydrochloric acid will be equal to 0.25 mol, since n (Zn):n (H 2) = 1:1, i.e. n(Zn) = n(H2). The mass of zinc (molar mass is 65 g/mol) is: m pure (Zn) = n (Zn) × M (Zn); m pure (Zn) = 0.25 × 65 = 16.25 g.
Answer	The mass of zinc is 16.25 g