Scientific Tutor

Example: What is the Δ n (delta n) of the equation below?

N_2(g) + 3 H_2(g) <—-> 2 NH_3(g)

Answer: Δ n = 2 – 4 = -2

VIDEO Calculating the DELTA N ( Δn ) Demonstrated Example 1: What is the Δn (delta n) of the equation below?

H₂SO_4(aq) <—–> H_2(aq) + S_(s) + 2 O_2(aq)

Add together all of the coefficients of the products that involve (aq) or (g) phases.

Answer: 1 H₂ + 2 O₂ = 3. (S is not counted because it is solid phase)

Add together all of the coefficients of the reactants that involve aq or g phases.

Answer: 1 H₂SO₄ = 1

Take the sum of the products minus the sum of the reactants.

Answer: 3 – 1 = 2

COMPLETE ANSWER: Δn = 2

VIDEO Calculating the DELTA N ( Δn ) Demonstrated Example 2: What is the Δn (delta n) of the equation below?  GIVE A NEGATIVE ANSWER

PRACTICE PROBLEMS: solve for the Δ n (delta n) in each problem.

What is the Δ n of the equation below?

MgBr_2(aq) + 2 NaI_(aq) <——> MgI_2(aq) + 2 NaBr_(aq)

Answer: 3 – 3 = Zero

What is the Δ n of the equation below?

2 H₂O_(g) <—-> 2 H_2(g) + O_2(g)

Answer: 3 – 2 = 1

What is the Δ n of the equation below?

2 Fe³⁺_(aq) + 3 CO₃^2-_(aq) <—-> Fe₂(CO₃)_3(s)

Answer: 0 – 5 = -5 don’t count Fe₂(CO₃)₃

What is the Δ n of the equation below?

C_4(s) + 4 O_2(g) <—-> 4 CO_2(g)

Answer: 4 – 4 = Zero don’t count C₄