(2 marks) Consider a student who is trying to calculate the concentration of nitrate ions in a solution. This solution

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(2 marks) Consider a student who is trying to calculate the
concentration of nitrate ions in a solution.

This solution was prepared first by adding together 150.0 mL of
0.100 M magnesium nitrate to 250.0 mL of 0.100 M aluminum(III)
nitrate. Then an additional 1.35 g of sodium nitrate was added to
give the final solution.

The student did the following steps:



Step 1: Calculate the moles of magnesium
nitrate in 150.0 mL of 0.100 M magnesium nitrate:

nmagnesium nitrate = (0.100 M)(0.1500 L) =
1.50 x 10-2 mol magnesium nitrate



Step 2: Calculate the moles of nitrate in the
magnesium nitrate:

nnitrate = 1.50 x 10-2 mol
magnesium nitrate x (1 nitrate / 1 magnesium nitrate) = 1.50 x
10-2 mol nitrate



Step 3: Calculate the moles of aluminum(III)
nitrate in 250.0 mL of 0.100 M aluminum(III) nitrate:

naluminum(III) nitrate = (0.100 M)(0.02500
L) = 2.50 x 10-3 mol aluminum(III) nitrate



Step 4: Calculate the moles of nitrate in the
aluminum(III) nitrate:

nnitrate = 2.50 x 10-3 mol
aluminum(III) nitrate x (3 nitrate / 1 aluminum(III) nitrate) =
7.50 x 10-3 mol nitrate



Step 5: Calculate the molar mass of sodium
nitrate:

mM = 22.990 g/mol + 14.007 g/mol + 3 x
15.999 g/mol = 84.994 g/mol



Step 6: Calculate the moles of sodium
nitrate:

nsodium nitrate = 1.35 g * 84.994 g/mol =
115 mol sodium nitrate



Step 7: Calculate the moles of nitrate in the
sodium nitrate:

n nitrate = 115 mol sodium nitrate x
(1 nitrate / 1 sodium nitrate) = 115 mol nitrate



Step 8: Calculate the total molarity of nitrate in
the solution:

Mnitrate = (1.50 x
10-2 mol nitrate + 7.50 x 10-3 mol
nitrate + 115 mol nitrate)/(0.1500 L + 0.2500 L) = 288 M
nitrate





Upon seeing this answer, the student knows they have made at least
one mistake.



Consider each individual step. If the student made an error in that
individual step indicate that YES there
is an error. If the step is completed correctly, then indicate
that NOthere is no error.




Yes No Step 1
Yes No Step 2
Yes No Step 3
Yes No Step 4
Yes No Step 5
Yes No Step 6
Yes No Step 7
Yes No Step 8