Chemical Equations and Balancing Questions in English

(N/A) $Magnesium$ is a very reactive metal. When stored,it reacts with oxygen to form a layer of $Magnesium$ $Oxide$ $(MgO)$ on its surface. This layer of $Magnesium$ $Oxide$ is quite stable and prevents further reaction of $Magnesium$ with oxygen. The $Magnesium$ ribbon is cleaned with sandpaper to remove this layer so that the underlying metal can be exposed to air for combustion.

(N/A) $(i)$ $H_{2(g)} + Cl_{2(g)} \longrightarrow 2HCl_{(g)}$
$(ii)$ $3BaCl_{2(aq)} + Al_{2}(SO_{4})_{3(aq)} \longrightarrow 3BaSO_{4(s)} + 2AlCl_{3(aq)}$
$(iii)$ $2Na_{(s)} + 2H_{2}O_{(l)} \longrightarrow 2NaOH_{(aq)} + H_{2(g)}$

(N/A) balanced chemical equation is one in which the number of atoms of each element is equal on both the reactant and product sides.
Chemical equations must be balanced to satisfy the $Law$ of $Conservation$ of $Mass$. This law states that mass can neither be created nor destroyed in a chemical reaction. Therefore,the total mass of the elements present in the reactants must be equal to the total mass of the elements present in the products. To ensure this,the number of atoms of each element must be the same on both sides of the equation.

(A) To balance a chemical equation,the number of atoms of each element must be equal on both the reactant and product sides.
$(a)$ $2HNO_{3} + Ca(OH)_{2} \longrightarrow Ca(NO_{3})_{2} + 2H_{2}O$
Here,there are $2$ $N$ atoms,$8$ $O$ atoms,$4$ $H$ atoms,and $1$ $Ca$ atom on both sides.
$(b)$ $2NaOH + H_{2}SO_{4} \longrightarrow Na_{2}SO_{4} + 2H_{2}O$
Here,there are $2$ $Na$ atoms,$6$ $O$ atoms,$4$ $H$ atoms,and $1$ $S$ atom on both sides.
$(c)$ $NaCl + AgNO_{3} \longrightarrow AgCl + NaNO_{3}$
This equation is already balanced as the number of atoms of each element is equal on both sides.
$(d)$ $BaCl_{2} + H_{2}SO_{4} \longrightarrow BaSO_{4} + 2HCl$
Here,there is $1$ $Ba$ atom,$2$ $Cl$ atoms,$2$ $H$ atoms,$1$ $S$ atom,and $4$ $O$ atoms on both sides.

(N/A) $Ca(OH)_{2} + CO_{2} \rightarrow CaCO_{3} + H_{2}O$
$(b)$ $Zn + 2AgNO_{3} \rightarrow Zn(NO_{3})_{2} + 2Ag$
$(c)$ $2Al + 3CuCl_{2} \rightarrow 2AlCl_{3} + 3Cu$
$(d)$ $BaCl_{2} + K_{2}SO_{4} \rightarrow BaSO_{4} + 2KCl$

(N/A) Oxidation is defined as the gain of oxygen by a substance during a chemical reaction.
For example:
$(i)$ $H_2 + CO_2 \rightarrow H_2O + CO$
In this reaction, $H_2$ gains oxygen to form $H_2O$, therefore $H_2$ is oxidized.
$(ii)$ $2Cu + O_2 \rightarrow 2CuO$
In this reaction, $Cu$ gains oxygen to form $CuO$, therefore $Cu$ is oxidized.

(N/A) Word equation: $\text{Sulphuric acid} + \text{Zinc} \rightarrow \text{Zinc sulphate} + \text{Hydrogen}$
Balanced equation: $H_2SO_{4(aq)} + Zn_{(s)} \rightarrow ZnSO_{4(aq)} + H_{2(g)}$
$(b)$ Word equation: $\text{Hydrochloric acid} + \text{Magnesium} \rightarrow \text{Magnesium chloride} + \text{Hydrogen}$
Balanced equation: $2HCl_{(aq)} + Mg_{(s)} \rightarrow MgCl_{2(aq)} + H_{2(g)}$

(N/A) Word equation: $\text{Sulphuric acid} + \text{Aluminium} \rightarrow \text{Aluminium sulphate} + \text{Hydrogen}$
Balanced equation: $3H_{2}SO_{4(aq)} + 2Al_{(s)} \rightarrow Al_{2}(SO_{4})_{3(aq)} + 3H_{2(g)}$
$(b)$ Word equation: $\text{Hydrochloric acid} + \text{Iron} \rightarrow \text{Iron(II) chloride} + \text{Hydrogen}$
Balanced equation: $Fe_{(s)} + 2HCl_{(aq)} \rightarrow FeCl_{2(aq)} + H_{2(g)}$

(A) The reaction between hydrogen gas $(H_2)$ and oxygen gas $(O_2)$ to form water $(H_2O)$ is a standard chemical reaction.
At room temperature and standard reaction conditions,hydrogen and oxygen exist as gases $(g)$.
When they react to form water,the product formed is liquid water $(l)$.
Therefore,the correct chemical equation representing the physical states is $2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$.

(A) To balance the equation $Fe(s) + H_2O(g) \rightarrow Fe_3O_4(s) + H_2(g)$:
$1$. Balance $Fe$: There are $3$ atoms of $Fe$ on the right side,so place a coefficient of $3$ before $Fe$ on the left side: $3Fe + H_2O \rightarrow Fe_3O_4 + H_2$.
$2$. Balance $O$: There are $4$ atoms of $O$ on the right side,so place a coefficient of $4$ before $H_2O$ on the left side: $3Fe + 4H_2O \rightarrow Fe_3O_4 + H_2$.
$3$. Balance $H$: Now there are $8$ atoms of $H$ on the left side $(4 \times 2)$,so place a coefficient of $4$ before $H_2$ on the right side: $3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)$.
The equation is now balanced.

(B) skeletal chemical equation is an unbalanced chemical equation in which the number of atoms of each element is not equal on both the reactant and product sides.
For example,the reaction $Mg + O_2 \rightarrow MgO$ is a skeletal equation because the number of oxygen atoms is not balanced.

(N/A) The balanced chemical equation for photosynthesis is:
$6CO_{2}(g) + 12H_{2}O(l) \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_{6}H_{12}O_{6}(aq) + 6O_{2}(g) + 6H_{2}O(l)$
Explanation:
$1$. $6$ molecules of carbon dioxide $(CO_{2})$ in gaseous state react with $12$ molecules of water $(H_{2}O)$ in liquid state.
$2$. The reaction occurs in the presence of sunlight and chlorophyll (the green pigment in plants).
$3$. The products formed are $1$ molecule of glucose $(C_{6}H_{12}O_{6})$ in aqueous state,$6$ molecules of oxygen $(O_{2})$ in gaseous state,and $6$ molecules of water $(H_{2}O)$ in liquid state.

(N/A) The chemical equation for the reaction between hydrogen gas and nitrogen gas to form ammonia is:
$3H_{2}(g) + N_{2}(g) \rightarrow 2NH_{3}(g)$
$(b)$ The chemical equation for the combustion of hydrogen sulphide gas in air (oxygen) to produce water and sulphur dioxide is:
$2H_{2}S(g) + 3O_{2}(g) \rightarrow 2H_{2}O(g) + 2SO_{2}(g)$

(N/A) The unbalanced equation is: $BaCl_{2} + Al_{2}(SO_{4})_{3} \longrightarrow AlCl_{3} + BaSO_{4}$.
To balance,we ensure the number of atoms of each element is equal on both sides: $3BaCl_{2}(aq) + Al_{2}(SO_{4})_{3}(aq) \longrightarrow 2AlCl_{3}(aq) + 3BaSO_{4}(s)$.
$(b)$ The unbalanced equation is: $K + H_{2}O \longrightarrow KOH + H_{2}$.
To balance,we ensure the number of atoms of each element is equal on both sides: $2K(s) + 2H_{2}O(l) \longrightarrow 2KOH(aq) + H_{2}(g)$.

(A) The chemical equation for the reaction is:
$AlCl_{3}(aq) + 3NH_{4}OH(aq) \longrightarrow Al(OH)_{3}(s) \downarrow + 3NH_{4}Cl(aq)$
Explanation:
$1$. Aluminium chloride $(AlCl_{3})$ reacts with ammonium hydroxide $(NH_{4}OH)$.
$2$. This is a double displacement reaction where aluminium hydroxide $(Al(OH)_{3})$ is formed as a gelatinous white precipitate,and ammonium chloride $(NH_{4}Cl)$ remains in the solution.
$3$. To balance the equation,we ensure the number of atoms of each element is equal on both sides: there is $1$ $Al$ atom,$3$ $Cl$ atoms,$3$ $N$ atoms,$15$ $H$ atoms,and $3$ $O$ atoms on both sides.

(N/A) The chemical reaction involves phosphorus $(P_4)$ reacting with chlorine gas $(Cl_2)$ to produce phosphorus pentachloride $(PCl_5)$.
The unbalanced equation is: $P_4 + Cl_2 \longrightarrow PCl_5$.
To balance the phosphorus atoms,we place a coefficient of $4$ before $PCl_5$: $P_4 + Cl_2 \longrightarrow 4PCl_5$.
To balance the chlorine atoms,we need $20$ chlorine atoms on the reactant side,so we place a coefficient of $10$ before $Cl_2$: $P_4(s) + 10Cl_2(g) \longrightarrow 4PCl_5(g)$.

(N/A) $(i)$ The reaction between manganese dioxide and aluminium is a thermite reaction: $3 MnO_{2} + 4 Al \longrightarrow 2 Al_{2}O_{3} + 3 Mn$
$(ii)$ The reaction of iron with steam produces iron($II$,$III$) oxide and hydrogen gas: $3 Fe(s) + 4 H_{2}O(g) \longrightarrow Fe_{3}O_{4}(s) + 4 H_{2}(g)$

(N/A) chemical equation is a symbolic representation of a chemical reaction,where the reactants and products are expressed using their respective chemical symbols and formulae.
An unbalanced chemical equation is known as a skeletal chemical equation.
It provides information about the reactants and products involved in the reaction but does not represent the actual number of atoms of each element on both sides of the equation,thus failing to satisfy the law of conservation of mass.

(A) To balance a chemical equation,the number of atoms of each element must be equal on both the reactant and product sides.
$(a)$ For $KClO_{3} \longrightarrow KCl + O_{2}$:
There is $1$ $K$,$1$ $Cl$,and $3$ $O$ on the left,and $1$ $K$,$1$ $Cl$,and $2$ $O$ on the right. To balance oxygen,we multiply $KClO_{3}$ by $2$ and $O_{2}$ by $3$. Then,to balance $K$ and $Cl$,we multiply $KCl$ by $2$. The balanced equation is: $2KClO_{3} \longrightarrow 2KCl + 3O_{2}$.
$(b)$ For $Na_{2}CO_{3} + HCl \longrightarrow NaCl + H_{2}O + CO_{2}$:
There are $2$ $Na$ atoms on the left,so we multiply $NaCl$ by $2$. This gives $2$ $Cl$ atoms on the right,so we multiply $HCl$ by $2$. Checking the atoms: $2$ $Na$,$1$ $C$,$3$ $O$,$2$ $H$,and $2$ $Cl$ on both sides. The balanced equation is: $Na_{2}CO_{3} + 2HCl \longrightarrow 2NaCl + H_{2}O + CO_{2}$.

(N/A) When aluminium is heated in air,it reacts with oxygen to form aluminium oxide.
The balanced chemical equation is: $4 Al + 3 O_{2} \rightarrow 2 Al_{2}O_{3}$.
The product formed is aluminium oxide $(Al_{2}O_{3})$.

(C) The reaction between hydrogen and oxygen to form water is a combustion reaction.
At standard reaction temperatures (often involving combustion),hydrogen $(H_2)$ and oxygen $(O_2)$ exist as gases $(g)$.
The product formed,water $(H_2O)$,is typically produced in the liquid state $(l)$ at room temperature or standard conditions following the reaction.
Therefore,the correct representation is $2H_2(g) + O_2(g) \longrightarrow 2H_2O(l)$.

(A) The statement is true.
Calcium oxide,with the chemical formula $CaO$,is commonly known as lime or quicklime. It is produced by the thermal decomposition of limestone $(CaCO_3)$.

$(A)$ The reaction between dinitrogen $(N_2)$ and dihydrogen $(H_2)$ is known as the Haber process.
In this process, one mole of nitrogen gas reacts with three moles of hydrogen gas to produce two moles of ammonia $(NH_3)$ gas.
The balanced chemical equation for this reaction is:
$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$
Therefore, the correct compound formed is ammonia.