2 nguyên tố cacbon.

2 nguyên tử cacbon.

2 đơn vị cacbon.

2 khối lượng cacbon

NaNO₃, phân tử khối là 85.

NaNO₃, phân tử khối là 86.

NaNO₂, phân tử khối là 69.

NaNO₃, phân tử khối là 100.

S₃O₁₂Al₂

Al₂(SO₄)₃

(SO₄)₃Al₂

S₃(O₆Al)₂

H₂, Cl₂, SO₂, N₂

H₂, N₂, SO₂, Cl₂

N₂, Cl₂, SO₂, H₂

H₂, SO₂, N₂, Cl₂

KCl, N₂, SO₂

Ba, O₂, Mg

NaCl, CaO, H₂SO₄

S, CO₂, H₂O

$$P\ +\ O_2\ \rightarrow\ P_2O_3$$  

$$4P\ +3O_2\ \rightarrow\ 2P_2O_3$$  

$$P_2\ +O_3\ \rightarrow P_2O_3$$  

$$6P\ +2O_2\ \rightarrow3P_2O_3$$  

$$Fe\ +\ 2HCl\ \rightarrow\ FeCl_2\ +\ H_2$$  

$$3Fe\ +\ 6HCl\ \rightarrow\ 3FeCl_2\ +\ H_2$$  

$$Fe\ +3HCl\ \rightarrow\ FeCl_2\ +\ 3H_2$$  

$$Fe\ +\ H_2Cl_3\ \rightarrow\ FeCl_3\ +\ H_2$$  

$$CuCl_2+2NaOH_{ }\ ->Cu\left(OH\right)_2+2NaCl$$  

$$3CuCl_2+NaOH_{ }\ ->3Cu\left(OH\right)_2+6NaCl$$  

$$CuCl_2+2NaOH_{ }\ ->Cu\left(OH\right)_2+NaCl$$  

$$CuCl_2+NaOH_{ }\ ->Cu\left(OH\right)_2+2NaCl$$  

$$Al_2(SO_4)_3+3BaCl_2\ ->2AlCl_3\ +3BaSO_4$$  

$$Al_2(SO_4)_3+2BaCl_2\ ->2AlCl_3\ +2BaSO_4$$  

$$Al_2(SO_4)_3+3BaCl_2\ ->AlCl_3\ +3BaSO_4$$  

$$2Al_2(SO_4)_3+BaCl_2\ ->4AlCl_3\ +BaSO_4$$