A 293.6-g sample of ground water is analyzed for calcium. The Ca2+ in the sample is first precipitated and filtered-off as NH4CaPO4·7H2O. This precipitate is dried and heated, releasing water and ammonia to yield anhydrous calcium pyrophosphate (Ca2P2O7). The mass of Ca2P2O7 obtained is 0.0833 g.

Give the calcium content of the ground water in parts per million

Can you explain why you changed 0.0002837g to 283.7g. The formula I have is (g solute/g solution) x 10^6 to find ppm. Also can you explain why you did 2 x 283.7? Is it to find the Calcium content because there are 2 of Ca?

To find the calcium content of the ground water in parts per million (ppm), follow these steps:

Step 1: Calculate the moles of Ca2P2O7 obtained.
First, calculate the molar mass of Ca2P2O7:
Ca = 40.08 g/mol
P = 30.97 g/mol
O = 16.00 g/mol

Molar mass of Ca2P2O7 = (2 × 40.08) + (2 × 30.97) + (7 × 16.00) = 222.08 g/mol

Next, calculate the number of moles of Ca2P2O7:
moles = mass / molar mass
moles = 0.0833 g / 222.08 g/mol

Step 2: Convert the moles of Ca2P2O7 to moles of calcium (Ca).
Since there is a 1:1 stoichiometric ratio between Ca2P2O7 and Ca, the number of moles of Ca is the same as the number of moles of Ca2P2O7.

Step 3: Convert the moles of Ca to mass of Ca in grams.
mass = moles × molar mass
mass = moles × 40.08 g/mol

Step 4: Convert the mass of Ca to parts per million (ppm).
ppm = (mass of Ca / mass of ground water) × 10^6

However, the mass of the ground water is not given in the question, so we cannot directly calculate the calcium content in parts per million without additional information.

To find the calcium content of the ground water in parts per million (ppm), we need to know the concentration of calcium ions in the water sample.

Given that the mass of the calcium pyrophosphate obtained is 0.0833 g, we can use the stoichiometry of the reaction to calculate the moles of calcium.

The balanced equation for the reaction is:
2 NH4CaPO4·7H2O + heat → Ca2P2O7 + 2 NH3 + 16 H2O

From the equation, we can see that 2 moles of NH4CaPO4·7H2O yield 1 mole of Ca2P2O7. Therefore, we need to convert the mass of Ca2P2O7 to moles.

Molar mass of Ca2P2O7 = 2(40.1 g/mol) + 2(31.0 g/mol) + 7(16.0 g/mol) = 222.1 g/mol

Moles of Ca2P2O7 = Mass of Ca2P2O7 / Molar mass of Ca2P2O7 = 0.0833 g / 222.1 g/mol

Next, we need to convert moles of Ca2P2O7 to moles of calcium (Ca). From the balanced equation, we can see that 1 mole of Ca2P2O7 contains 2 moles of Ca.

Moles of Ca = Moles of Ca2P2O7 × (2 moles of Ca / 1 mole of Ca2P2O7)

Finally, to determine the calcium concentration in parts per million, we need to know the volume of the water sample. Let's assume it is 1 liter (1000 ml) for simplicity.

Calcium concentration in ppm = (Moles of Ca / Volume of water sample in liters) × 10^6

Substitute the calculated values into the equation, and you will have the calcium content in parts per million for the given ground water sample.

0.0833g Ca2P2O7/293.6 g sample = 0.0002837 g Ca2P2O7/1 g sample = 283.7 g/1,00,000 g sample = 283.7 ppm Ca2P2O7 = 2 x 283.7 ppm NH4CaPO4.7H2O = 567.4 ppm in the water