# 0.1 Stoichiometry: laws to moles to molarity  (Page 3/3)

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## Materials list

3M hydrochloric acid (HCl) solution

sodium bicarbonate ${\text{NaHCO}}_{3}$

methyl orange indicator

## Part 2

• Ask you TA for your assigned molarity–it will range from 0.7 M to 1.2 M.
• First need to know the formula for the solute.
• Need the molecular weight of the solute in g/mole.
• The volume of solution, 100 mLs.
• Remember to ensure that all the solute is dissolved before finally filling with deionised water to the mark on the volumetric flask.
• Take your solution to your TA to check the molarity by titration, record value on your report form and your percent error.

## Pre-lab 2: stoichiometry

(Total 10 points)

Click here to print the Pre-Lab Note: In preparing this Pre-Lab you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

1) Which one of the following is a correct expression for molarity?

A) mol solute/L solvent

B) mol solute/mL solvent

C) mmol solute/mL solution

D) mol solute/kg solvent

E)μmol solute/L solution

2) What is the concentration (M) of KCl in a solution made by mixing 25.0 mL of 0.100 M KCl with 50.0 mL of 0.100 M KCl?

A) 0.100

B) 0.0500

C) 0.0333

D) 0.0250

E) 125

3) How many grams of ${\text{CH}}_{3}\text{OH}$ must be added to water to prepare 150 mL of a solution that is 2.0 M ${\text{CH}}_{3}\text{OH}$ ?

A) 9.6× ${\text{10}}^{3}$

B) 4.3× ${\text{10}}^{2}$

C) 2.4

D) 9.6

E) 4.3

4) The concentration of species in 500 mL of a 2.104 M solution of sodium sulfate is __________ M sodium ion and __________ M sulfate ion.

A) 2.104, 1.052

B) 2.104, 2.104

C) 2.104, 4.208

D) 1.052, 1.052

E) 4.208, 2.104

5) Oxalic acid is a diprotic acid. Calculate the percent of oxalic acid ${H}_{2}{C}_{2}{O}_{4}$ in a solid given that a 0.7984 g sample of that solid required 37.98 mL of 0.2283 M NaOH for neutralization.

A) 48.89

B) 97.78

C) 28.59

D) 1.086

E) 22.83

6) A 31.5 mL aliquot of ${H}_{2}{\text{SO}}_{4}$ (aq) of unknown concentration was titrated with 0.0134 M NaOH (aq). It took 23.9 mL of the base to reach the endpoint of the titration. The concentration (M) of the acid was __________.

A) 0.0102

B) 0.0051

C) 0.0204

D) 0.102

E) 0.227

7) What are the respective concentrations (M) of ${\text{Fe}}^{3+}$ and ${I}^{-}$ afforded by dissolving 0.200 mol ${\text{FeI}}_{3}$ in water and diluting to 725 mL?

A) 0.276 and 0.828

B) 0.828 and 0.276

C) 0.276 and 0.276

D) 0.145 and 0.435

E) 0.145 and 0.0483

8) A 36.3 mL aliquot of 0.0529 M ${H}_{2}{\text{SO}}_{4}$ (aq) is to be titrated with 0.0411 M NaOH (aq). What volume (mL) of base will it take to reach the equivalence point?

A) 93.6

B) 46.8

C) 187

D) 1.92

E) 3.84

9) A 13.8 mL aliquot of 0.176 M ${H}_{3}{\text{PO}}_{4}$ (aq) is to be titrated with 0.110 M NaOH (aq). What volume (mL) of base will it take to reach the equivalence point?

A) 7.29

B) 22.1

C) 199

D) 66.2

E) 20.9

10) A solution is prepared by adding 1.60 g of solid NaCl to 50.0 mL of 0.100 M ${\text{CaCl}}_{2}$ . What is the molarity of chloride ion in the final solution? Assume that the volume of the final solution is 50.0 mL.

A) 0.747

B) 0.647

C) 0.132

D) 0.232

E) 0.547

## Report 2: stoichiometry

(Total 80 points)

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code). This is only an advisory template of what needs to be include in your complete lab write-up.

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

## Data table

 Mass Grams empty 150-mL beaker ${\text{NaHCO}}_{3}\text{in beaker}$ ${\text{Mass of NaHCO}}_{3}$
 Mass Grams NaCl plus beaker first weighing NaCl plus beaker second weighing NaCl plus beaker third weighing

1) The grams of ${\text{NaHCO}}_{3}$ you had in your beaker was ________

2) Calculate how many moles of ${\text{NaHCO}}_{3}$ the mass is ________

3) Write the molar ratio for the ${\text{NaHCO}}_{3}$ / NaCl ratio _______

4) Write the number of moles of NaCl you predict were produced in your experiment.

5) Calculate the mass of NaCl you predict will be produced.

6) Determine, by subtraction, the actual mass of NaCl produced in your experiment.

a) first weighing

b) second weighing

c) third weighing

## Discussion questions

1. Compare the numerical value of the observed ratio for maximum yield to the best ratio

## Part 2

Complete the equation for the titration of

${\text{NaHCO}}_{3\text{aq}}+{\text{HCl}}_{\text{aq}}\to$

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