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

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## Materials list

100 mls volumetric flask

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__________________________

Circle the correct answer:

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

7) Calculate your percentage yield.

## Discussion questions

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

## Part 2

Record your TAs value of the molarity of your solution.

Calculate your percent error from your assigned value.

Complete the equation for the titration of

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

#### Questions & Answers

can someone help me with some logarithmic and exponential equations.
sure. what is your question?
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
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or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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Stotaw
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Azam
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At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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how did you get the value of 2000N.What calculations are needed to arrive at it
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