Please help ASAP Mass of crucible + cover _____ Mass of crucible + cover + unkno
ID: 490383 • Letter: P
Question
Please help ASAP Mass of crucible + cover _____ Mass of crucible + cover + unknown _____ Mass of unknown _____ Mass of crucible + cover + unknown, after heating _____ Mass of unknown, after heating _____ Mass change of sample upon heating _____ The sample is a carbonate salt a hydrogen carbonate salt (Circle one) Mass of crucible + cover + solid chloride _____ Mass of chloride _____ Q = (mass of final chloride - mass of original unknown)/mass of original unknown = _____ (note this is the experimental value of Q) Theoretical Values of O: for sodium salt: if the sample was a sodium compound its formula is _____ g of compound will produce _____ grams of NaCI Theoretical Q for sodium compound = _____ for potassium salt: if the sample was a potassium compound its formula is _____ g of compound will produce _____ grams of KCI Theoretical Q for potassium compound = _____ Now compare your experimental Q value to the theoretical Q values - which one is the experimental Q closest to? This identifies your unknown. Unknown number: _____ Formula of Unknown: _____
Explanation / Answer
Mass of crucible + cover = 23.52g
Mass of crucible +cover + unknown = 24.56g
Mass of unknown = 24.56g - 23.52g = 1.04g
Mass of crucible + cover + unknown (after heating) = 24.42g
Mass of unknown after heating = 24.42g - 23.52g = 0.9g
Mass change of sample upon heating = 1.04g - 0.9g = 0.14g
If the compound is carbonate salt, the sample will lose between 0.01 and 0.04g of mass. If it is a hydrogen carbonate salt, there will be a significant loss of mass, greater than 0.1g.
So, unknown is a hydrogen carbonate salt, as the mass change of sample is 0.14g.
mass of crucible + cover + solid chloride = 24.45g
mass of solid chloride = 24.45g - 23.52g = 0.93g
Q = (mass of final chloride - mass of original unknown) / mass of original unknown
Q = 0.93g-1.04g / 1.04g = 0.1058 (experimental value of Q)
Now, calculate theoretical values of Q as folllows:
For sodium salt: if the sample was a sodium compound its formula is NaHCO3.
84.01g of NaHCO3 will produce 58.44g of NaCl.
Theoretical Q for sodium compound = (58.44g NaCl - 84.01g NaHCO3)/84.01g NaHCO3 = 0.3044
For potassium salt: if the sample was a potassium compound its formula is KHCO3.
100.12g KHCO3 will produce 74.55g of KCl.
Theoretical Q for potassium compound = (74.55g KCl - 100.12g KHCO3)/100.12g KHCO3 = 0.2554
now compare experimental Q value (0.1058) to the theoretical Q values.
As the experimental Q value (0.1058) is closer to theoretical Q (0.2554) of KHCO3. So the unknown compound is potassium hydrogen carbonate.