50 cm3 of NaOH was added to the acid. What is this volume in dm3?

1000 cm3 = 1 dm3 50 cm3 / 1000 = 0.050 dm3

1 Moles 2 Flashcards by Shanon Garcia

A solution of HCl is 1 M

What does the M stand for?

M stands for Molar

M = mole / dm³

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Rearrange the concentration equation in terms of moles

n = C V

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What volume does 0.5 moles of chlorine gas occupy?

12 dm³

V = n x molar volume = 0.5 mole x 24dm³/mol = 12dm³

1 mole of any gas occupies 24dm³

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50 cm³ of NaOH was added to the acid.

What is this volume in dm³?

1000 cm³ = 1 dm³

50 cm³ / 1000 = 0.050 dm³

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Why must we use a burette when titrating?

It allows us to measure any amount of acid/alkali with a small uncertainty. We can also add drop by drop near the end point (neutralisation point)

This burette - if used properly - measures to +- 0.1 cm³

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How many moles are there in 24 dm³ of carbon dioxide gas?

1 mole of carbon dioxide molecules

1 mole of any gas occupies 24dm³ at room temp

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During titration, why must we use a pipette to measure out the solution into the conical flask?

Using a pipette decreases the uncertainty in our volume reading

If this pipette is used properly it measures to +- 0.03 cm³ !!

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What colour is methyl orange in acid and alkali?

red in acid

yellow in alkali

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What is the relationshipe between moles, mass and RFM

moles = mass/ RFM

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Define concentration

Concentration is moles per unit volume of a solution

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Why must you swirl your conical flask during titration?

To fully mix the acid and alkali - ensure that the reaction is complete.

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Does using a pipette and burette which both measure volume to a high resolution improve the accuracy or reliability of your results?

Using a pipette and burette and reading these at eye level and to the bottom of the meniscus improves the accuracy of your results.

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Read the burette below

42.30 cm³

Do not forget to add the zero - you can tell if it is exactly on the 0.30 or if it is 0.35!!

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What do we call the process of filling a burette on the floor using a funnel?

This is called ‘charging’ the burette

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What colour is litmus in alkali?

blue

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2H₂ + O₂ ⇒ 2H₂O

What volume of oxygen is needed to fully react with 30 dm³ of hydrogen?

2H₂ + 1O₂ ⇒ 2H₂O

15dm³of oxygen

1 mole of any gas occupies the same volume- therefore use the short cut!

Mole ratio of H₂ : O₂ is 2 : 1

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What are concordant results?

Concordant results are when the volume of solution added are within 0.2 cm³ of each other.

Any concordant results are then averaged.

What colour is litmus in acid?

red

25.00 cm³ of sodium hydroxide was added to a conical flask. 10.0 cm³ of 2M hydrochloric acid was needed to neutralise the sodium hydroxide.

Calculate the moles of HCl used.

n = CV

n = 2M x 0.010 dm³=0.02 mol

20.00 cm³ of sodium hydroxide was added to a conical flask. 10.0 cm³ of 2M hydrochloric acid was needed to neutralise the sodium hydroxide.

n = CV

n = 2M x 0.010 dm3 =0.02 mol of acid was used

HCl : NaOH is a 1:1 mole ratio

Therefore 0.02 mol of NaOH reacted

Calculate the concentration of NaOH?

C = n/V

C = 0.02 / 0.020 = 1 mol/dm³OR 1M

Name the equipment below

A- volumetric flask

B- pipette

C- burette

What steps do you follow when calculating the concentration of an acid needed to neutralise a known concentration of alkali?

Use n = CV to find moles of alkali
Use mole ratio between acid and alkali from balanced equation
used C = n/V to find concentration of acid

DO NOT FORGET - VOLUME MUST BE IN dm³

What volume does 1 moles of ammonia gas occupy?

24 dm³

V = n x molar volume = 1 mol x 24dm³/mol= 24dm³

1 mole of any gas occupies 24dm³

2H₂ + O₂ ⇒ 2H₂O

What volume of hydrogen is needed to fully react with 20 dm³ of oxygen?

2H₂ + 1O₂ ⇒ 2H₂O

40dm³of hydrogen

1 mole of any gas occupies the same volume- therefore use the short cut!

Mole ratio of O₂ : H₂ is 1 : 2

How many moles are there in 48dm³ of oxygen gas?

2 moles of oxygen molecules n = V / molar volume = 48 dm³ / 24dm³/mol = 2 mol **1 mole of any gas occupies 24dm3 at room temp**

Rearrange the concentration equation in term of volume

V = n / C

How can a 2M solution of sulfuric acid be used to make a 0.2M solution of sulfuric acid?

Pipette _10 cm³_ of 2M sulfuric acid and place it into a _100cm³_ volumetric flask. Fill the volumetric flask with distilled water so that the bottom of the meniscus is at the marked line on the neck of the flask.

What volume does 2 moles of argon gas occupy?

48 dm³ V = n x molar volume = 2 mol x 24dm³/mol = 48dm³ 1 mole of _any gas_ occupies 24dm³

What colour is phenolphthalein in alkali?

pink

2H₂ + O₂ ⇒ 2H₂O What _volume of water vapour_ is produced from **70 dm³** **of hydrogen**?

**2**H₂ + O₂ ⇒ **2**H₂O **70dm³of water vapour** 1 mole of any gas occupies the same volume- therefore use the short cut! Mole ratio of H₂ : H₂O is 2 : 2

10 000 cm³ of acid was added to the mixture. What is this in dm³?

1000cm³ = 1 dm³ 10 dm³

How do you get a burette ready for titration?

1. place the burette on the floor 2. make sure that the tap is closed 3. fill the burette with the acid/alkali using a funnel 4. place a beaker under the burette and open the tap to allow the air bubble to pass 5. DO NOT FORGET TO RECORD THE INITIAL VOLUME OF ACID/ALKALI BEFORE TITRATING

What is molar volume

Molar volume is the volume of one mole of gas at room temperature Molar volume = 24 dm³ / mol

Does repeating a titration to get similar results improve the accuracy or reliablility of the results?

repeating makes the results more reliable reliable = repeatable

How many moles are there in 24dm³ of hydrogen gas?

1 mole of hydrogen molecules 1 mole of any gas occupies 24dm³ at room temp

What is the relationship between moles, molar volume and volume of a gas?

moles = volume / molar volume

What is the equation that links concentration, moles and volume?

25.00 cm³ of sodium hydroxide was added to a conical flask. 10.0 cm³ of 2M hydrochloric acid was needed to neutralise the sodium hydroxide. n = CV n = 2M x 0.010 dm³ =0.02 mol of acid was used How many moles of sodium hydroxide reacted with 0.02 mol of acid?

Use mole ratio NaOH : HCl 1 : 1 Therefore, 0.02 moles of sodium hydroxide reacted

Why is an indicator needed during titration?

Titration uses the neutralisation of a known concentration of an acid/alkali to find the concentration of an unknown concentration of acid/alkali. At neutralisation there are equal moles of H⁺ ions from the acid and OH^- ions from the alkali. An indicator is used to find this neutralisation point by providing an observable colour change.

What colour is phenolphthalein in acid?

colourless