First, write down the first half of the skeleton equation (what you already know)
Cr (s) HCl (aq) >
Second, figure out what type of reaction this is. As there is one metal (chromium) and two non-metals (Hydrogen and Chlorine), it is a single replacement reaction meaning that one of the non metals will bond with the metal. To figure out which one will will bond with chromium, look at the ion charges. Chromium has a positive ion charge, chlorine has a negative ion charge, and hydrogen has a positive ion charge. As opposites attract, Chlorine will bond with chromium in this reaction. To figure out the compound, look at the ion charges. You dont state whether youre dealing with chromium (II) or Chromium (III) so Ill do both. You need to find how many atoms of the element with the lower ion charge are needed to match the ion charge of the other. Also, hydrogen is a diatomic molecule so when its on its own, it is always H2.
Cr (s) HCl (aq) > CrCl3 (aq) H2 (g)
or
Cr (s) HCl (aq) > CrCl2 (aq) H2 (g)
Next, you need to balance the equation (make the number of atoms of each element on each side equal) First, find the number of atoms on each side of the skeleton equation.
For chromium (II) and hydrochloric acid, there is 1 chromium atom, 2 hydrogen atoms, and 1 Chlorine atom on the left side, and 1 chromium atom, 2 chlorine atoms, and 1 hydrogen atom on the right side. To balance this, place a coefficient of 2 in front of HCl to match the number of chlorine atoms and hydrogen atoms on each side.
Cr (s) 2 HCl (aq) > CrCl2 (aq) H2 (g)
That is the balanced equation for chromium (II).
For chromium (III) and Hydrochloric acid, there is 1 chromium atom, 1 hydrogen atom, and 1 Chlorine atom on the left side, and 1 chromium atom, 3 chlorine atoms, and 2 hydrogen atoms on the right side. To balance this, place a coefficient of 3 in front of HCl to match the number of chlorine atoms on each side.
Cr (s) 3 HCl (aq) > CrCl3 (aq) H2 (g)
Now the hydrogens are uneven so double what you already have
2 Cr (s) 6 HCl (aq) > 2 CrCl3 (aq) 2 H2 (g)
And change the coefficient from a 2 to a 3 in front of the hydrogen on the right to match it with the left side.
2 Cr (s) 6 HCl (aq) > 2 CrCl3 (aq) 3 H2 (g)
Thats the balanced equation for chromium (III)
So, to sum it up, here are the word, skeleton, and balanced equations for Chromium (II) and Hydrochloric acid; and Chromium (III) and Hydrochloric acid. Numerals in square brackets do not need to be included (I included them for clarity).
Word: Chromium [(II)] Hydrochloric acid = Chromium (II) Chloride Hydrogen
Skeleton: Cr (s) HCl (aq) > CrCl2 (aq) H2 (g)
Balanced: 2 Cr (s) 4 HCl (aq) > 2 CrCl2 (aq) 2 H2 (g)
Word: Chromium [(III)] Hydrochloric acid > Chromium (III) Chloride Hydrogen
Skeleton: Cr (s) HCl (aq) > CrCl3 (aq) H2 (g)
Balanced: 2 Cr (s) 6 HCl (aq) > 2 CrC3 (aq) 3 H2 (g)
First, write down the first half of the skeleton equation (what you already know)
Cr (s) HCl (aq) >
Second, figure out what type of reaction this is. As there is one metal (chromium) and two non-metals (Hydrogen and Chlorine), it is a single replacement reaction meaning that one of the non metals will bond with the metal. To figure out which one will will bond with chromium, look at the ion charges. Chromium has a positive ion charge, chlorine has a negative ion charge, and hydrogen has a positive ion charge. As opposites attract, Chlorine will bond with chromium in this reaction. To figure out the compound, look at the ion charges. You dont state whether youre dealing with chromium (II) or Chromium (III) so Ill do both. You need to find how many atoms of the element with the lower ion charge are needed to match the ion charge of the other. Also, hydrogen is a diatomic molecule so when its on its own, it is always H2.
Cr (s) HCl (aq) > CrCl3 (aq) H2 (g)
or
Cr (s) HCl (aq) > CrCl2 (aq) H2 (g)
Next, you need to balance the equation (make the number of atoms of each element on each side equal) First, find the number of atoms on each side of the skeleton equation.
For chromium (II) and hydrochloric acid, there is 1 chromium atom, 2 hydrogen atoms, and 1 Chlorine atom on the left side, and 1 chromium atom, 2 chlorine atoms, and 1 hydrogen atom on the right side. To balance this, place a coefficient of 2 in front of HCl to match the number of chlorine atoms and hydrogen atoms on each side.
Cr (s) 2 HCl (aq) > CrCl2 (aq) H2 (g)
That is the balanced equation for chromium (II).
For chromium (III) and Hydrochloric acid, there is 1 chromium atom, 1 hydrogen atom, and 1 Chlorine atom on the left side, and 1 chromium atom, 3 chlorine atoms, and 2 hydrogen atoms on the right side. To balance this, place a coefficient of 3 in front of HCl to match the number of chlorine atoms on each side.
Cr (s) 3 HCl (aq) > CrCl3 (aq) H2 (g)
Now the hydrogens are uneven so double what you already have
2 Cr (s) 6 HCl (aq) > 2 CrCl3 (aq) 2 H2 (g)
And change the coefficient from a 2 to a 3 in front of the hydrogen on the right to match it with the left side.
2 Cr (s) 6 HCl (aq) > 2 CrCl3 (aq) 3 H2 (g)
Thats the balanced equation for chromium (III)
So, to sum it up, here are the word, skeleton, and balanced equations for Chromium (II) and Hydrochloric acid; and Chromium (III) and Hydrochloric acid. Numerals in square brackets do not need to be included (I included them for clarity).
Word: Chromium [(II)] Hydrochloric acid = Chromium (II) Chloride Hydrogen
Skeleton: Cr (s) HCl (aq) > CrCl2 (aq) H2 (g)
Balanced: 2 Cr (s) 4 HCl (aq) > 2 CrCl2 (aq) 2 H2 (g)
Word: Chromium [(III)] Hydrochloric acid > Chromium (III) Chloride Hydrogen
Skeleton: Cr (s) HCl (aq) > CrCl3 (aq) H2 (g)
Balanced: 2 Cr (s) 6 HCl (aq) > 2 CrC3 (aq) 3 H2 (g)
2Cr 6HCl> 2CrCl3 3H2
2Cr 6HCl> 2CrCl3 3H2
This post is last updated on hrtanswers.com at Date : 1st of September – 2022