A .972g sample of a Cacl2 2H2O/K2C2O4 H2O solid salt mixture is dissolved in 150 ml of deionized water, previously adjusted to a pH that is basic . The precipitate after having been filtered and air dried has a mass of .375g. what is the percent by mass of CaCl2 2H2O
I think it would help you if you wrote the equation and balanced it first thing. I assume you can do that.
The ppt is CaC2O4 and it has a mass of 0.375.
Convert that to moles CaC2O4, then to moles CaCl2.2H2O(using the coefficients in the balanced equation), then to grams CaCl2.2H2O.
Finally, %CaCl2.2H2O = (mass from the above/mass sample initially)*100 = ??
mass sample initially was 0.972 g.
To find the percent by mass of CaCl2 2H2O in the solid salt mixture, you need to calculate the mass of CaCl2 2H2O that was originally present in the mixture.
1. Determine the mass of the precipitate (m_precipitate) after filtration and air drying, which is given as 0.375g.
2. Calculate the mass of CaCl2 2H2O in the original sample:
- Since the precipitate is solely composed of CaCl2 2H2O, the mass of CaCl2 2H2O in the precipitate (m_cacl2_2h2o) is equal to the mass of the precipitate.
- Therefore, m_cacl2_2h2o = 0.375g.
3. Calculate the percent by mass of CaCl2 2H2O in the solid salt mixture:
- The percent by mass is calculated by dividing the mass of CaCl2 2H2O by the initial mass of the sample and multiplying by 100.
- Since the sample mass is not provided, we'll calculate it based on the given information.
- The mass of the sample is the sum of the mass of the precipitate and the mass of the remaining salt mixture before precipitation.
- Thus, we can calculate the mass of the remaining salt mixture (m_salt_mixture) by subtracting the mass of the precipitate from the initial mass of the sample:
m_salt_mixture = mass of the sample - m_cacl2_2h2o.
- However, mass of the sample = mass of the filtrate (water) + mass of the precipitate, according to the conservation of mass.
- The mass of the filtrate is not provided, but we know it is the mass of the original sample minus the mass of the precipitate:
mass of the filtrate = mass of the sample - m_precipitate.
- Therefore, we can rewrite the mass of the salt mixture as:
m_salt_mixture = (mass of the sample - m_precipitate) - m_cacl2_2h2o.
4. Once you have the calculated value for m_salt_mixture, the percent by mass of CaCl2 2H2O can be calculated as follows:
percent by mass = (m_cacl2_2h2o / (m_cacl2_2h2o + m_salt_mixture)) * 100.
By following these steps and performing the necessary calculations, you can find the percent by mass of CaCl2 2H2O in the solid salt mixture.