A 20.29 g sample of impure MgCO3 is completely decomposed at 1000oC in previously evacuated 2.0 L reaction vessel. After the reaction was complete the solid residue had a mass of 15.9 g. Assume that only MgCO3 could produce gas CO2 what percent of original sample was magnesium carbonate? What was the pressure of the CO2 produced?

Do I use PV/T = PV/T to find this answer? Thank you for helping!

You need to start from the chemical equation for the decompostion of MgCO3.

Assuming that all the CO2 resulted from the conposition of MgCO3, the mass difference tells you the mass of CO2 produced and hence the number of moles of CO2. The number of moles of CO2 can be used to
a) calculate the number of moles of MgCO3 decomposed (using the chemical equation). From the number of moles of MgCO3 calculate the mass of MgCO3 decomposed from which you can calculate the percentage of MgCO3 in the original sample.
b) I assume that the question is asking for the pressure at 1000oC. You can use
PV/T = PV/T
by assuming that 1 mole of any gas occupies 22.4 litres at STP. This give you the LHS values. For the RHS, V=2.0 L and T=1000oC (convert to kelvin), P we are trying to find.

Hope that this helps.

To find the percent of the original sample that was magnesium carbonate, you need to compare the mass of the magnesium carbonate before and after the reaction.

1. Calculate the mass of the magnesium carbonate before the reaction:
Mass of the impure MgCO3 = 20.29 g

2. Calculate the mass of the magnesium carbonate after the reaction:
Mass of the solid residue = 15.9 g

3. Calculate the mass of CO2 released during the reaction:
Mass of CO2 released = Mass of impure MgCO3 - Mass of solid residue

4. Calculate the percent of original sample that was magnesium carbonate:
Percent of magnesium carbonate = (Mass of CO2 released / Mass of impure MgCO3) * 100%

Now, let's move on to calculating the pressure of the CO2 produced:

To find the pressure of the CO2 produced, you can use the Ideal Gas Law formula, PV = nRT, where:
- P is the pressure of the gas
- V is the volume of the gas (2.0 L)
- n is the number of moles of the gas
- R is the ideal gas constant (0.0821 L·atm/(mol·K))
- T is the temperature in Kelvin (1000oC = 1273.15 K)

However, before we can use the Ideal Gas Law, we need to determine the number of moles of CO2 produced:

5. Calculate the number of moles of CO2 produced using the mass of CO2:
Moles of CO2 = (Mass of CO2 released / molar mass of CO2)

The molar mass of CO2 (carbon dioxide) is 44.01 g/mol.

Once you have the number of moles of CO2, you can substitute the values into the Ideal Gas Law:

6. Rearrange the Ideal Gas Law equation to solve for P:
P = (n * R * T) / V

Substitute the values of n (moles of CO2), R (ideal gas constant), T (temperature in Kelvin), and V (volume) into the equation to find the pressure of the CO2 produced.

Remember to convert the temperature to Kelvin (add 273.15) before plugging it into the equation.

By following these steps, you can find both the percent of the original sample that was magnesium carbonate and the pressure of the CO2 produced.