Group 1A and 2A Reactions - Online Tutor, Practice Problems & Exam Prep

• Group 1A and 2A metals react violently with water, producing hydrogen gas and a metal hydroxide, which is a highly exothermic reaction.
• In the reaction of Group 1A metals with water, the metal reacts to form hydrogen gas, a metal ion with a +1 charge, and hydroxide ions.
• For Group 2A metals reacting with water, the metal would form a +2 charged metal ion.
• Both Group 1A and 2A metals react with halogens from Group 7A to form ionic halides.
• Group 1A metals react with diatomic halogens to produce ionic halides with a simple 1:1 stoichiometry, balancing the charges of +1 (metal) and -1 (halogen).
• Group 2A metals react with halogens to form ionic halides with a 1:2 stoichiometry, reflecting the +2 charge of the metal and the -1 charge of each halogen atom.
• Balancing the chemical equations is necessary in both types of reactions to ensure the conservation of mass and charge.

Reaction with H2O

Here we're going to say that alkaline metals, the elements in Group 1A and alkaline earth metals from group 2A, undergo numerous reactions. Now, the two types of reactions that we're going to pay attention to are those that have them reacting with either water or a halogen from group 7A.

Now here we take a look at the reaction with water. We're going to say both groups react violently with water and have high exothermic, so ΔH of hydration. Now recall when metals react with an acidic proton H₂ gas is formed. Here we have an example of a reaction of these metals with water and in particular we're looking at group 1A.

Now with group 1A, we're going to say that arm metal from group 1A reacts with water. It's going to generate H₂ gas. In addition to this, it would produce our metal ion, and since it's in Group 1A, it's plus one. If we're in Group 2A, it'd be +2 plus hydroxide ion, and we said that this is a highly exothermic reaction.

Remember, exothermic means we're releasing heat, so heat would be a product. Once we balance this out, we'd have to put a 2 here, here, here and here, and this would represent my balanced equation between the reaction of group 1A metal with water. Now remember M here could stand in for a group 1/8 or a group 28 metal.

Group 1A and 2A Reactions Example

Here it says we need to complete and balance the following reaction. So from group 18 we have potassium solid reacting with liquid water. Now from our example that we saw earlier, we know that this will produce H₂ gas.

We know that it will produce 2 moles of potassium ion aqueous, it will produce 2 hydroxide ions aqueous plus the generation of heat. It is an exothermic process, so heat would be a product.

Now in addition to this we'd have a 2 here and A₂ here to finish balancing out our reaction O. This would represent our complete imbalance reaction between the reaction between the reacting of potassium solid and liquid water.

Alkaline earth metals react with certain substances to produce hydrogen gas. Which of the following will result in hydrogen gas formation? Provide a balanced reaction.

a) Beryllium (Be) and O₂

b) Barium (Ba) and CO₂

c) Calcium (Ca) and H₂O

d) Strontium (Sr) and O₂

• A. Beryllium (Be) and O₂
  2 Be(s) + O₂(g) → 2 BeO(s)
• B. Barium (Ba) and CO₂
  Ba(s) + 2 CO₂(g) → BaO(s) + CO(g) + heat
• C. Calcium (Ca) and H₂O
  Ca(s) + 2 H₂O(l) → H₂(g) + Ca²⁺(aq) + 2 OH^–(aq) + heat
• D. Strontium (Sr) and O₂
  2 Sr(s) + O₂(g) → 2 SrO(s)

Reaction with Halogens

Now when it comes to the reaction with halogens, we're going to say both groups 1A and 2A react with halogens to produce ionic pallets. If we take a look here, if M here represents a group 1A metal, it reacts with a diatomic halogen to produce an ionic halid. Remember, group 1A is plus one in charge. Halogens are in Group 7A, so they're -1. The numbers are the same, so they just cancel out. So our ionic halid is MX.

We have to balance this out. There's two halogens here, but only one here. So I throw 2 here. But now I have two metals on the product side, so I'd have to put a 2 here. M could also represent a group 2A metal which have a charge of two plus or +2. They would still react with the halogen, which is -1 and create M2X2 solid as a product.

In that case, you get that as a product and you still have to balance out your overall reaction if necessary. So just remember group 1A and 2A metals react with diatomic halogens to produce ionic halts.

Group 1A and 2A Reactions Example

Here it's us to complete and balance the following reaction. Here we have lithium salt reactor with diatomic fluorine gas. So if we know here that lithium is in Group 1A, so it's plus one fluorine in Group 7-8, so it's -1. As a result, we create lithium fluoride.

We still have to balance this reaction, so I put a 2 here. So both sides have two fluorines and I'd have to put a 2 here so that both sides have two lithiums. This would represent our complete and balanced reaction between lithium fluoride well between lithium solid and fluorine gas into production of lithium fluoride.

2   Li (s) +   F 2   (g)   →   2   LiF (s)

Provide the products from the reaction between strontium and aqueous chlorine.

• A. SrCl(s)
• B. Sr₂Cl₃(s)
• C. Sr₂Cl(s)
• D. SrCl₂(s)