Hydrogen Cyanide, HCN, is a poisonous gas. The lethal dose is approximately
300mg HCN per kilogram of air when inhaled.
If the HCN is formed by the reaction of NaCN with an acid such as H2SO4,
what mass of NaCN gives the lethal dose in the room from the previous
question?
2NCN (s) + H2SO4 (aq) - Na2S04 (aq) + 2HCN (g)

mass of NaCN = 0.539 g

Further explanation

A reaction coefficient is a number in the chemical formula of a substance involved in the reaction equation. The reaction coefficient is useful for equalizing reagents and products.

Reaction

2NaCN (s) + H₂SO₄ (aq) ⇒ Na₂S0₄ (aq) + 2HCN (g)

MW HCN = 27,0253 g/mol

MW NaCN = 49,0072 g/mol

Assume there is 1 kg air, and mass of HCN = 300 mg

mol HCN :

mass 300 mg = 0.3 g

NaCN : HCN = 2 : 2(mole ratio from equation), so :

mol NaCN = mol HCN = 0.011

mass NaCN :

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.