Question

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Explanation:

Step1: Count H atoms on each side

Left: $H_2$ has 2 H atoms; Right: $HCl$ has 1 H atom, with coefficient 2, so total 2 H atoms.

Step2: Count Cl atoms on each side

Left: $Cl_2$ has 2 Cl atoms; Right: $HCl$ has 1 Cl atom, with coefficient 2, so total 2 Cl atoms.

Step3: Balance H₂ coefficient

To match 2 H atoms on left, coefficient of $H_2$ is 1.

Step4: Balance Cl₂ coefficient

To match 2 Cl atoms on left, coefficient of $Cl_2$ is 1.

Answer:

1 $H_2$ + 1 $Cl_2$ → 2 $HCl$