# cr + hcl

Cr + 2HClCrCl2 + H2

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### Word Equation

Chromium + Hydrogen Chloride = Chromous Chloride + Dihydrogen

One mole of

Chromium [Cr]

and two moles of

Hydrogen Chloride [HCl]

react to tát form one mole of

Chromous Chloride [CrCl2]

and one mole of

Dihydrogen [H2]

### Thermodynamics

Thermodynamics of the reaction can be calculated using a lookup table.

#### Is the Reaction Exothermic or Endothermic?

Cr (g) HCl (g) CrCl2 (s) 1 mol 397.48 kJ/mol -397.48 kJ 2 mol -92.29904 kJ/mol 184.59808 kJ 1 mol -395.388 kJ/mol -395.388 kJ 1 mol 0 kJ/mol 0 kJ 212.88192 kJ -395.388 kJ -608.26992 kJ

ΣΔH°f(reactants) > ΣΔH°f(products), so sánh Cr + HCl = CrCl2 + H2 is exothermic (releases heat).

#### Is the Reaction Exoentropic or Endoentropic?

ΔS = Sproducts - Sreactants. If ΔS < 0, it is exoentropic. If ΔS > 0, it is endoentropic.

Cr (g) HCl (g) CrCl2 (s) 1 mol 174.22176 J/(mol K) -174.22176 J/K 2 mol 186.77376 J/(mol K) -373.54752 J/K 1 mol 115.31104 J/(mol K) 115.31104 J/K 1 mol 130.586824 J/(mol K) 130.586824 J/K 547.76928 J/K 245.897864 J/K -301.871416 J/K

ΣΔS°(reactants) > ΣΔS°(products), so sánh Cr + HCl = CrCl2 + H2 is exoentropic (decrease in entropy).

#### Is the Reaction Exergonic or Endergonic?

ΔG = Gproducts - Greactants. If ΔG < 0, it is exergonic. If ΔG > 0, it is endergonic.

Cr (g) HCl (g) CrCl2 (s) 1 mol 352.58568 kJ/mol -352.58568 kJ 2 mol -95.31152 kJ/mol 190.62304 kJ 1 mol -356.0584 kJ/mol -356.0584 kJ 1 mol 0 kJ/mol 0 kJ 161.96264 kJ -356.0584 kJ -518.02104 kJ

ΣΔG°(reactants) > ΣΔG°(products), so sánh Cr + HCl = CrCl2 + H2 is exergonic (releases energy).

### Reaction Expressions

Kc or Q = ( [CrCl2] [H2] ) / ( [Cr] [HCl]2 )

(assuming all reactants and products are aqueous. substitutue 1 for any solids/liquids, and Psubstance for gases.)

rate = -(Δ[Cr] / Δt) = -1/2 * (Δ[HCl] / Δt) = (Δ[CrCl2] / Δt) = (Δ[H2] / Δt)

(assuming constant volume in a closed system and no accumulation of intermediates or side products)

## Instructions

To balance a chemical equation, enter an equation of a chemical reaction and press the Balance button. The balanced equation will appear above.

• Use uppercase for the first character in the element and lowercase for the second character. Examples: Fe, Au, Co, Br, C, O, N, F.
• Ionic charges are not yet supported and will be ignored.
• Replace immutable groups in compounds to tát avoid ambiguity. For example, C6H5C2H5 + O2 = C6H5OH + CO2 + H2O will not be balanced, but XC2H5 + O2 = XOH + CO2 + H2O will.
• Compound states [like (s) (aq) or (g)] are not required.
• You can use parenthesis () or brackets [].

## How To Balance Equations

Read our article on how to tát balance chemical equations or ask for help in our chat.

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## Balance Cr + HCl = CrCl2 + H2 Using the Algebraic Method To balance the equation Cr + HCl = CrCl2 + H2 using the algebraic method step-by-step, you must have experience solving systems of linear equations. The most common methods are substitution/elimination and linear algebra, but any similar method will work.

1. ### Label Each Compound With a Variable

Label each compound (reactant or product) in the equation with a variable to tát represent the unknown coefficients.

a Cr + b HCl = c CrCl2 + d H2

2. ### Create a System of Equations

Create an equation for each element (Cr, H, Cl) where each term represents the number of atoms of the element in each reactant or product.

Cr: 1a + 0b = 1c + 0d H: 0a + 1b = 0c + 2d Cl: 0a + 1b = 2c + 0d

3. ### Solve For All Variables

Use substitution, Gaussian elimination, or a calculator to tát solve for each variable.

• 1a - 1c = 0
• 1b - 2d = 0
• 1b - 2c = 0

Use your graphing calculator's rref() function (or an online rref calculator) to tát convert the following matrix into reduced row-echelon-form:

[ 1 0 -1 0 0] [ 0 1 0 -2 0] [ 0 1 -2 0 0]

The resulting matrix can be used to tát determine the coefficients. In the case of a single solution, the last column of the matrix will contain the coefficients.

Simplify the result to tát get the lowest, whole integer values.

• a = 1 (Cr)
• b = 2 (HCl)
• c = 1 (CrCl2)
• d = 1 (H2)
4. ### Substitute Coefficients and Verify Result

Count the number of atoms of each element on each side of the equation and verify that all elements and electrons (if there are charges/ions) are balanced.

Cr + 2 HCl = CrCl2 + H2

Reactants Products Cr 1 1 ✔️ 2 2 ✔️ 2 2 ✔️

Since there is an equal number of each element in the reactants and products of Cr + 2HCl = CrCl2 + H2, the equation is balanced.

## Balance Cr + HCl = CrCl2 + H2 Using Inspection

The law of conservation of mass says that matter cannot be created or destroyed, which means there must be the same number atoms at the kết thúc of a chemical reaction as at the beginning. To be balanced, every element in Cr + HCl = CrCl2 + H2 must have the same number of atoms on each side of the equation. When using the inspection method (also known as the trial-and-error method), this principle is used to tát balance the one element at a time until both sides are equal and the chemical equation is balanced.

### 1. Count the number of each element on the left and right hand sides

Reactants (Left Hand Side)Products (Right Hand Side)
ReactantsProducts
CrHClTotalCrCl2H2Total
Cr1111✔️
H1122
Cl1122

### 2. Multiply coefficients for compounds to tát balance out each element

1. H is not balanced. Add 1 molecule(s) of HCl to tát the reactant (left-hand) side to tát balance Hydrogen: Cr + 2HCl = CrCl2 + H2

ReactantsProducts
Cr11✔️
H22✔️
Cl22✔️

### 3. Verify that the equation is balanced

Since there are an equal number of atoms of each element on both sides, the equation is balanced.

Cr + 2HCl = CrCl2 + H2

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