Milk of magnesia, a suspension of Mg(OH)2 in water, reacts with stomach acid (HCl) in a neutralization reaction.

Question

1.Milk of magnesia, a suspension of Mg(OH)2in water, reacts with stomach acid (HCl) in a neutralization reaction.

Mg(OH)2(s) + 2 HCl(aq) −→

2 H2O(l) + MgCl2(aq) What mass of MgCl2 will be produced if

5.49 g of Mg(OH)2 reacts? Answer in units of g.

2.What mass of HCl is required to completely react with 5.49 g of Mg(OH)2?

Answer in units of g.

Answer 1

Write a correctly balanced equation for this reaction:

Mg(OH)₂(s) + 2HCl(aq) ==> MgCl₂(aq) + 2H₂O(l)

What mass of MgCl₂ is produced if 5.49 g of Mg(OH)₂ reacts? This assumes that HCl is present in excess.

5.49 g Mg(OH)₂ x 1 mole/58.3 g = 0.0942 moles Mg(OH)₂

0.0942 moles Mg(OH)₂ x 1 mole MgCl₂/1 mole Mg(OH)₂ = 0.0942 moles MgCl₂ produced

Mass of MgCl₂ produced = 0.0942 moles x 95.2 g/mole = 8.96 g MgCl₂

What mass of HCl is required?

0.0942 moles Mg(OH)₂ x 2 moles HCl/mole Mg(OH)₂ = 0.188 moles HCl

Mass of HCl = 0.188 moles x 36.5 g/mole = 6.88 g HCl