Question

1. complete the following single replacement and double replacement reactions:
2. mg + hcl →
3. na + agno₃ →

Explanation:

Step1: Analyze the first reaction (Mg + HCl)

Magnesium (Mg) is a metal and hydrochloric acid (HCl) is an acid. In single - replacement reactions, a more reactive metal can replace a less reactive element in a compound. Magnesium is more reactive than hydrogen. So, Mg will replace H in HCl. The reaction produces magnesium chloride ($MgCl_2$) and hydrogen gas ($H_2$). The unbalanced equation is $Mg + HCl
ightarrow MgCl_2 + H_2$. To balance it, we need 2 moles of HCl for 1 mole of Mg. So the balanced equation is $Mg + 2HCl = MgCl_2 + H_2\uparrow$.

Step2: Analyze the second reaction (Na + $AgNO_3$)

Sodium (Na) is a very reactive metal. In a single - replacement reaction, sodium will replace silver (Ag) in silver nitrate ($AgNO_3$) because sodium is more reactive than silver. The products will be sodium nitrate ($NaNO_3$) and silver (Ag). The unbalanced equation is $Na+AgNO_3
ightarrow NaNO_3 + Ag$. This equation is already balanced in terms of atoms of Na, Ag, N, and O. But we should also consider the reactivity of sodium with water (if the reaction is in aqueous solution). However, for the purpose of a simple single - replacement reaction at the basic level, we can write the reaction as $Na + AgNO_3=NaNO_3 + Ag$. But in reality, sodium reacts vigorously with water in the aqueous solution of $AgNO_3$ to produce $NaOH$ and $H_2$, and then $NaOH$ reacts with $AgNO_3$ to produce $AgOH$ (which quickly decomposes to $Ag_2O$) and $NaNO_3$. But for the initial learning of single - replacement reactions, the simple form is acceptable.

Answer:

1. $\boldsymbol{Mg + 2HCl = MgCl_2 + H_2\uparrow}$
2. $\boldsymbol{Na + AgNO_3 = NaNO_3 + Ag}$ (Note: In an aqueous environment, the reaction is more complex due to Na's reaction with water, but this is the basic single - replacement form.)