Chapter 1. ChemTutor Problem

1.1 Problem Statement

Question 1.1

qAaRYI/q90MQnHl4XYnXY8BBylXEGD0HTb7kJ68TLixRRZoB1LKQw7oORuhVA7gMW2EDu887VghbxDc3uymDt6HUL9boMC6FVSDJHV+BaK3igTrxPnFQ1vPi6zpx9j+JfIRQWQ/308aGhFHopUNKWihQypO/XquUroX55emVM8y4kqzrniwcOAaxOGb4ZDFjNk6HWv7sH7oUz6bgjxnUB7xT/rZ6fon0ER3J8enjXSy4EcJrvHqzrDC+IdliqWc3J4NO1eJGQa4AIom7dA+bwJMUdLbEG+yp1ov46fZKahLZsKelh+ehYBMxzOHPJjbUlcZxVQ==
Correct.
Incorrect.
{qqMC1 == 0} 1.2 I’m sorry, that is not correct. Remember that the molar mass of a compound is the sum of the molar masses of all the atoms in one molecule or formula unit of the compound. Since the molar masses of atoms are positive values, a compound cannot have a negative molar mass.
{qqMC1 == 3} 1.3 I’m sorry, that is not correct. Have you balanced the chemical reaction equation?
{qqMC1 == 2} 1.4 I’m sorry, that is not correct. To convert from moles of NaOH delivered to moles of H2A reacted, you must use the correct mole ratio derived from the stoichiometric coefficients in the balanced chemical equation. Since you need the moles of NaOH to cancel, the correct mole ratio is 1 mol H2A/2 mol NaOH.
{help} 1.5 We'll guide you through how to solve this problem.

1.2 Molar Mass

Here are some resources to help you better understand molar mass.

  • Link to ebook 3.6, 3.11
  • Link to a problem from 3.6/3.11

Question 1.2

We'll ask a simple problem here: 0VV1JcqyBrI=

Correct.
Incorrect.

1.3 Stoichiometry

Question 1.3

Consider the following equation:

H2A(aq) + NaOH(aq) -> Na2A(aq) + H2O(l)

Balance the equation by entering the appropriate numbers (Don't leave any spaces blank - use 1 if needed):

0VV1JcqyBrI=H2A(aq) + XvVM00l89Is=NaOH(aq) -> 0VV1JcqyBrI=Na2A(aq) + XvVM00l89Is=H20(l)

Correct. You should consider this stoichiometry when they try the original problem again.
Incorrect.

How do I calculate the moles of NaOH that react?

Notice that you are given the molar concentration and volume of NaOH delivered in the titration. Since the units of molar concentration (molarity) are in moles/L, multiplying the molar concentration by the volume of NaOH (in L) yields the moles of NaOH.

Question 1.4

How many moles of NaOH react?XvVM00l89Is=

Correct.
Incorrect. Link to section 4.6

How do I calculate the moles of H2A that react?

Once you have the moles of NaOH delivered in the titration, use the stoichiometric coefficients to derive the mole ratio to convert from moles NaOH to moles H2A. Since you need the moles of NaOH to cancel, the correct mole ratio is 1 mol H2A/2 mol NaOH.

Question 1.5

How many moles of H2A react? 0VV1JcqyBrI=

Correct.
Incorrect. Link to section 4.3

How do I calculate the molar mass from the moles of H2A that react?

The units of molar mass are g/mol. Inspect the question and notice that you are given the mass of the H2A sample. Next, divide the mass of H2A by the moles of H2A.

Question 1.6

I'm not sure exactly what this question should be 0VV1JcqyBrI=

Correct.
Incorrect. Link to section 4.3

1.4 Inverted mole ratio

Any additional help to provide?