Sodium cyanide is very useful in inorganic chemistry since the cyanide anion has a high affinity for metals, especially with gold.

What is the molar mass of this compound?

Calculate the percent composition by mass for each element in sodium cyanide.

How many carbon atoms are found in 1.2 pounds of solution if the solution is 5.0% sodium cyanide by mass?

(1.0 pound = 4.5 x 10² g)

Question

Sodium cyanide is very useful in inorganic chemistry since the cyanide anion has a high affinity for metals, especially with gold.

What is the molar mass of this compound?

Calculate the percent composition by mass for each element in sodium cyanide.

How many carbon atoms are found in 1.2 pounds of solution if the solution is 5.0% sodium cyanide by mass?

(1.0 pound = 4.5 x 10² g)

| General Chemistry 1

Accepted Answer

Sodium cyanide: NaCN ⇒ M_NaCN = M_Na + M_C + M_N = 23.0 + 12.0 + 14.0 = 49.0 g.mol^-1

% composition by mass:

% Na = M_Na/ M_NaCN x 100 = 23.0 / 49.0 x 100 = 46.9%

% C = 24.5%

% N = 28.6 %

Number of carbon atoms N:

n_C = N / N_A

Because we have only one carbon atom in the molecule NaCN: n_C = n_NaCN = m_NaCN/ M_NaCN

m_NaCN = 1.2 pounds x (4.5 x 10²) g / 1 pound x 0.050 = 2.7 x 10 g

N = N_A x n_C = N_A x n_NaCN = N_A x m_NaCN/ M_NaCN = 6.022 x 10²³ x 2.7 x 10 / 49.0 = 3.3 x 10²³ atoms

Midterm 1 - Question 6 | General Chemistry 1