To extract gold from its ore, the ore is treated with sodium cyanide solution in the presence of oxygen and water.

4 Au(s) + 8 NaCN(aq) + O2(g) + 2 H2O(l) 4 NaAu(CN)2(aq) + 4 NaOH(aq)

(a) Determine the mass of gold that can be extracted if 29.3 g sodium cyanide is used.

(b) If the mass of the ore from which the gold was extracted is 146.5 g, what percentage of the ore is gold?

To answer these questions, we need to use stoichiometry and molar mass calculations. Let's start with part (a).

(a) Determine the mass of gold that can be extracted if 29.3 g sodium cyanide is used.

To find the mass of gold, we need to calculate the moles of sodium cyanide (NaCN) used and then use the stoichiometry of the balanced chemical equation to find the moles of gold (Au) produced. Finally, we can convert the moles of gold into grams.

1. Calculate the moles of NaCN:
To do this, we need the molar mass of NaCN, which is the sum of the atomic masses of sodium (Na), carbon (C), and nitrogen (N).

Molar mass of NaCN = (molar mass of Na) + (molar mass of C) + (molar mass of N)
= (22.99 g/mol) + (12.01 g/mol) + (14.01 g/mol)
= 49.01 g/mol

Now, we can calculate the moles of NaCN:
Moles of NaCN = Mass of NaCN / Molar mass of NaCN
= 29.3 g / 49.01 g/mol
= 0.598 mol (rounded to three decimal places)

2. Use the stoichiometry of the balanced chemical equation to find the moles of Au:
From the balanced chemical equation, we can see that 4 moles of Au are produced for every 8 moles of NaCN used.

Moles of Au = (Moles of NaCN) × (4 mol Au / 8 mol NaCN)
= 0.598 mol × (4 mol / 8 mol)
= 0.299 mol (rounded to three decimal places)

3. Convert the moles of Au into grams:
To do this, we need the molar mass of Au, which is the atomic mass of gold.

Molar mass of Au = 196.97 g/mol

Mass of Au = (Moles of Au) × (Molar mass of Au)
= 0.299 mol × 196.97 g/mol
= 59.0 g (rounded to one decimal place)

Therefore, the mass of gold that can be extracted if 29.3 g of sodium cyanide is used is approximately 59.0 grams.

(b) If the mass of the ore from which the gold was extracted is 146.5 g, what percentage of the ore is gold?

To answer this question, we need to calculate the percentage of gold in the ore.

Percentage of gold in the ore = (Mass of gold / Mass of ore) × 100

Substituting the given values:

Percentage of gold in the ore = (59.0 g / 146.5 g) × 100
= 40.2%

Therefore, approximately 40.2% of the ore is gold.

(a) 58.87 g

all I know!