Problem: A sample of 5.55 g of Mg(OH)2 is added to 25.2 mL of 0.180 M HNO3.How many moles of Mg(NO3)2 are present after the reaction is complete?

FREE Expert Solution

We’re being asked to determine the number of moles of Mg(NO3)2 produced after a sample of 5.55 g Mg(OH)2 is added to 25.2 mL of 0.180 M HNO3.


Recall that molarity is the ratio of the moles of solute and the volume of solution (in liters). In other words:


Molarity (M)=moles of soluteLiters of solution


For this problem, we need to do the following steps:

Step 1: Write and balance a chemical equation for the given reaction.

Step 2: Determine the moles of the reactants

Step 3: Determine the moles of Mg(NO3)2 produced 


Step 1: Write and balance a chemical equation for the given reaction.

Since Mg(OH)2 and HNOare ionic compounds, they form ions when dissociating in water. 


The dissociation of the two compounds is as follows:

For HNO3: Hydrogen is from Group 1 so it has a charge of +1. Nitrate is a polyatomic ion that has a charge of  –1:

HNO3 (aq)  H+(aq) + NO3(aq)


For Mg(OH)2: Magnesium is from Group 2 so it has a charge of +2. The hydroxide ion has a charge of –1:

Mg(OH)2(aq)  Mg2+(aq) + 2 OH(aq)


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Problem Details

A sample of 5.55 g of Mg(OH)2 is added to 25.2 mL of 0.180 M HNO3.

How many moles of Mg(NO3)2 are present after the reaction is complete?

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