Question

1. draw the lewis structure diagrams for the following molecular compounds. a. nitrogen gas b. dihydrogen monoxide
2. balance each of the following equations and state which type of reaction it is. make sure you show your work
3. ___h₂o + → 2h₂ + 2o₂ type: single displacement
4. _ki + _pb(no₃)₂ → _pbi₂ + _kno₃ type: ___
5. _h₂ + _n₂ → _nh₃ type: _

predict the products of these chemical reactions. write the balanced

1. _hcl + _mg(oh)₂ → type: ___

the complete combustion of propane (c₃h₈)

Explanation:

Step1: Balance the equation $\mathrm{H_2O}\to\mathrm{H_2}+\mathrm{O_2}$

We need to balance the oxygen atoms first. Since there are 2 oxygen atoms on the right - hand side (in $\mathrm{O_2}$) and 1 on the left - hand side (in $\mathrm{H_2O}$), we put a 2 in front of $\mathrm{H_2O}$. Then, to balance the hydrogen atoms, we put a 2 in front of $\mathrm{H_2}$. The balanced equation is $2\mathrm{H_2O}\to2\mathrm{H_2}+\mathrm{O_2}$. This is a decomposition reaction as one compound breaks down into two simpler substances.

Step2: Balance the equation $\mathrm{KI}+\mathrm{Pb(NO_3)_2}\to\mathrm{PbI_2}+\mathrm{KNO_3}$

For the iodine atoms, we have 2 iodine atoms in $\mathrm{PbI_2}$, so we put a 2 in front of $\mathrm{KI}$. Then, for the potassium and nitrate ions, we put a 2 in front of $\mathrm{KNO_3}$. The balanced equation is $2\mathrm{KI}+\mathrm{Pb(NO_3)_2}\to\mathrm{PbI_2}+2\mathrm{KNO_3}$. This is a double - displacement reaction as the cations and anions of two different compounds exchange places.

Step3: Balance the equation $\mathrm{H_2}+\mathrm{N_2}\to\mathrm{NH_3}$

We have 2 nitrogen atoms in $\mathrm{N_2}$ and 1 in $\mathrm{NH_3}$, so we put a 2 in front of $\mathrm{NH_3}$. Then, to balance the hydrogen atoms, we put a 3 in front of $\mathrm{H_2}$. The balanced equation is $3\mathrm{H_2}+\mathrm{N_2}\to2\mathrm{NH_3}$. This is a synthesis reaction as two simpler substances combine to form a more complex one.

Step4: Predict and balance the reaction $\mathrm{HCl}+\mathrm{Mg(OH)_2}\to$

This is an acid - base neutralization reaction. The products are $\mathrm{MgCl_2}$ and $\mathrm{H_2O}$. For the chlorine atoms, since there are 2 chlorine atoms in $\mathrm{MgCl_2}$, we put a 2 in front of $\mathrm{HCl}$. Then, for the hydrogen and oxygen atoms, we need 2 moles of $\mathrm{H_2O}$. The balanced equation is $2\mathrm{HCl}+\mathrm{Mg(OH)_2}\to\mathrm{MgCl_2}+2\mathrm{H_2O}$.

Step5: Write the complete combustion of propane $\mathrm{C_3H_8}$

The products of the complete combustion of a hydrocarbon are carbon dioxide ($\mathrm{CO_2}$) and water ($\mathrm{H_2O}$). First, balance the carbon atoms. Since there are 3 carbon atoms in $\mathrm{C_3H_8}$, we put a 3 in front of $\mathrm{CO_2}$. Then, for the hydrogen atoms, since there are 8 hydrogen atoms in $\mathrm{C_3H_8}$, we put a 4 in front of $\mathrm{H_2O}$. Finally, for the oxygen atoms, we have $3\times2 + 4\times1=10$ oxygen atoms on the right - hand side. So we put a 5 in front of $\mathrm{O_2}$. The balanced equation is $\mathrm{C_3H_8}+5\mathrm{O_2}\to3\mathrm{CO_2}+4\mathrm{H_2O}$. This is a combustion reaction.

Answer:

1. $2\mathrm{H_2O}\to2\mathrm{H_2}+\mathrm{O_2}$, Decomposition
2. $2\mathrm{KI}+\mathrm{Pb(NO_3)_2}\to\mathrm{PbI_2}+2\mathrm{KNO_3}$, Double - displacement
3. $3\mathrm{H_2}+\mathrm{N_2}\to2\mathrm{NH_3}$, Synthesis
4. $2\mathrm{HCl}+\mathrm{Mg(OH)_2}\to\mathrm{MgCl_2}+2\mathrm{H_2O}$, Neutralization
5. $\mathrm{C_3H_8}+5\mathrm{O_2}\to3\mathrm{CO_2}+4\mathrm{H_2O}$, Combustion