Which of the following is a single replacement?

a. KOH + HCl --> KCl + H2O
b. 2Na + 2H2O --> H2 + 2NaOH
c. 2C2H6 + 7O2 --> 4CO2 + 6H2O
d. H2O + CO2 --> H2CO3

Any help would be appreciated, thank you in advance!

a. K goes with Cl and H goes with OH so this is a double replacement.

b. Na is a single item, it replaces ther H of H2O so this is a single replacement.
c. This is a combustion reaction
d. When two somethings combine to make one something that is a combination or synthesis reaction.

A single replacement reaction involves one element replacing another element in a compound. In the given chemical equations, option a and d are not single replacement reactions as they involve the rearrangement or combination of elements without any direct replacement.

Option b involves the displacement of hydrogen from water (H2O) by sodium (Na) to form sodium hydroxide (NaOH) and hydrogen gas (H2). This is a single replacement reaction.

Option c involves the combustion of ethane (C2H6) in the presence of oxygen (O2) to form carbon dioxide (CO2) and water (H2O). This is a combustion reaction and not a single replacement reaction.

Therefore, the correct answer is option b: 2Na + 2H2O --> H2 + 2NaOH.

To determine which of the given chemical equations represents a single replacement reaction, we need to understand what a single replacement reaction is.

In a single replacement reaction, also known as a displacement reaction, one element replaces another element in a compound. This occurs when a more reactive element displaces a less reactive element from its compound.

Let's analyze each equation to identify if it represents a single replacement reaction:

a. KOH + HCl --> KCl + H2O - This equation does not involve a single element replacing another element in a compound. It is a neutralization reaction between an acid (HCl) and a base (KOH), forming a salt (KCl) and water (H2O).

b. 2Na + 2H2O --> H2 + 2NaOH - This equation does not involve a single replacement either. It is a reaction between sodium (Na) and water (H2O) to form hydrogen gas (H2) and sodium hydroxide (NaOH). No element is replacing another element.

c. 2C2H6 + 7O2 --> 4CO2 + 6H2O - This equation represents the combustion of ethane (C2H6). It is not a single replacement reaction but a combustion reaction where ethane reacts with oxygen (O2) to form carbon dioxide (CO2) and water (H2O).

d. H2O + CO2 --> H2CO3 - This equation represents the reaction between water (H2O) and carbon dioxide (CO2) to form carbonic acid (H2CO3). It is not a single replacement reaction.

Therefore, none of the given options represents a single replacement reaction.

it should be "b"