One kilogram of Gold ore containing 190 ppm of Gold is dissolved in 2500.00 ml of NaCN solution. Calculate the molarity of Au in the solution

To find the molarity of gold (Au) in the solution after dissolving one kilogram of gold ore containing 190 ppm (parts per million) of gold, we need to follow a few logical steps. Let's break it down together.

Understanding the Components

First, we need to clarify what 190 ppm means. This indicates that there are 190 grams of gold in one million grams of the ore. Since we have one kilogram (or 1000 grams) of gold ore, we can calculate the amount of gold present in that sample.

Calculating the Amount of Gold

Using the definition of ppm, we can set up a proportion:

• 190 grams of gold in 1,000,000 grams of ore
• Let x be the grams of gold in 1,000 grams of ore.

We can set up the equation:

x = (190 grams / 1,000,000 grams) × 1,000 grams = 0.19 grams of gold.

Converting Grams to Moles

Next, we need to convert grams of gold to moles. The molar mass of gold (Au) is approximately 197 g/mol. To find the number of moles of gold, we use the formula:

Number of moles = mass (grams) / molar mass (g/mol)

Substituting in our values:

Number of moles of Au = 0.19 grams / 197 g/mol ≈ 0.000964 moles.

Calculating Molarity

Molarity (M) is defined as the number of moles of solute (in this case, gold) per liter of solution. We have dissolved the gold in 2500.00 mL of NaCN solution. First, we need to convert milliliters to liters:

2500.00 mL = 2.500 L.

Now we can calculate the molarity:

Molarity (M) = moles of solute / liters of solution

Substituting in our values:

Molarity of Au = 0.000964 moles / 2.500 L ≈ 0.0003856 M.

Final Result

Thus, the molarity of gold (Au) in the NaCN solution is approximately 0.000386 M. This value indicates the concentration of gold in the solution, which is essential for understanding how much gold is available for further chemical reactions or processes.