1. A student attempts to identify an unknown compound by the method used in this

Question

1. A student attempts to identify an unknown compound by the method used in this experiment. She finds that when she heated a sample weighing 0.4862 g the mass barely changed, dropping to 0.4855 g. When the product was converted to a chloride, the mass went up, to 0.5247 g.

a. Is the sample a carbonate? NO

b. What are the two compounds that might be in the unknown? KHCO3 and NaHCO3

c. Write the chemical equation for the overall reaction that would occur when the original compound was converted to a chloride. If the compound is a hydrogen carbonate, use the sum of Reactions 1 and 2. If the sample is a carbonate, use Reaction 2. Write the equation for a sodium salt and then for a potassium salt.

d. How many moles of the chloride salt would be produced from one mole of original compound? _____

e. How many grams of the chloride salt would be produced from one molar mass of original compound? Molar masses: NaHCO3 84.008 g Na2CO3 105.99 g NaCl 58.44 g KHCO3 100.118 g K2CO3 138.21 g KCl 74.55 g

If a sodium salt, ____________ g original compound ____________ g chloride I

f a potassium salt, ____________ g original compound ____________ g chloride

f. What is the theoretical value of Q, if she has an Na salt? ____________ if she has a K salt? ____________

g. What was the observed value of Q? ____________

h. Which compound did she have as an unknown?

I have bolded my own answers. I need help with the rest, please show work!

Explanation / Answer

d.

1 mol of chloride salt would be formed from 1 mol of bicarbonate.

2 mol of chloride salt would be formed from 1 mol of carbonate.

e.

1 mol NaHCO3 weighs 84 g can form 1 mol of NaCl which weighs 58.5 g (decrease in the mass)

1 mol KHCO3 weighs 100 g can form 1 mol of KCl which weighs 74.5 g (increase in the mass)

1 mol Na2CO3 weighs 106 g can form 2 mol of NaCl which weighs 117 g (decrease in the mass)

1 mol K2CO3 weighs 138 g can form 2 mol of KCl which weighs 149 g ((increase in the mass)

0.4862 g NaHCO3 can form 0.3386 g NaCl

0.4862 g Na2CO3 can form 0.5367 g NaCl

0.4862 g KHCO3 can form 0.3622 g KCl

0.4862 g K2CO3 can form 0.5247 g KCl

f.

Q is 0.5367 g if she has Na salt

Q is 0.5247 g if she has K salt

g. The observed value of Q is: 0.5247 g

h. The compound she has is K2CO3

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.