26.5k views
5 votes
When potassium cyanide (KCN) reacts with acids, a deadly poisonous gas, hydrogen cyanide (HCN), is given off: KCN(aq) + HCl(aq) → HCN(g) + KCl(aq) If a sample of 0.420 g of KCN is treated with an excess of HCl, calculate the amount of HCN formed in grams.

1 Answer

4 votes

Answer: The mass of hydrogen cyanide formed is 0.17 grams

Step-by-step explanation:

To calculate the number of moles, we use the equation:


\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}} .....(1)

Given mass of KCN = 0.420 g

Molar mass of KCN = 65.12 g/mol

Putting values in equation 1, we get:


\text{Moles of KCN}=(0.420g)/(65.12g/mol)=0.0064mol

The given chemical equation follows:


KCN(aq.)+HCl(aq.)\rightarrow HCN(g)+KCl(aq.)

As, hydrochloric acid is present in excess. So, it is considered as an excess reagent.

Thus, potassium cyanide is a limiting reagent because it limits the formation of products.

By Stoichiometry of the reaction:

1 mole of potassium cyanide produces 1 mole of hydrogen cyanide.

So, 0.0064 moles of potassium cyanide will produce =
(1)/(1)* 0.00064=0.0064mol of hydrogen cyanide

Now, calculating the mass of hydrogen cyanide from equation 1, we get:

Molar mass of HCN = 27.02 g/mol

Moles of HCN = 0.0064 moles

Putting values in equation 1, we get:


0.0064mol=\frac{\text{Mass of HCN}}{27.02g/mol}\\\\\text{Mass of HCN}=0.17g

Hence, the mass of hydrogen cyanide formed is 0.17 grams

User Souvikc
by
8.1k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.