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RGS 5th Form Chemistry CH-F > 1 Moles 2 > Flashcards

1 Moles 2 Flashcards

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1
Q

A solution of HCl is 1 M

What does the M stand for?

A

M stands for Molar

M = mole / dm3

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2
Q

Rearrange the concentration equation in terms of moles

A

n = C V

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3
Q

What volume does 0.5 moles of chlorine gas occupy?

A

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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4
Q

50 cm3 of NaOH was added to the acid.

What is this volume in dm3?

A

1000 cm3 = 1 dm3

50 cm3 / 1000 = 0.050 dm3

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5
Q

Why must we use a burette when titrating?

A

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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6
Q

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

A

1 mole of carbon dioxide molecules

1 mole of any gas occupies 24dm3 at room temp

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7
Q

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

A

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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8
Q

What colour is methyl orange in acid and alkali?

A

red in acid

yellow in alkali

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9
Q

What is the relationshipe between moles, mass and RFM

A

moles = mass/ RFM

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10
Q

Define concentration

A

Concentration is moles per unit volume of a solution

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11
Q

Why must you swirl your conical flask during titration?

A

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

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12
Q

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

A

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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13
Q

Read the burette below

A

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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14
Q

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

A

This is called ‘charging’ the burette

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15
Q

What colour is litmus in alkali?

A

blue

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16
Q

2H2 + O2 ⇒ 2H2O

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

A

2H2 + 1O2 ⇒ 2H2O

15dm3 of 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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17
Q

What are concordant results?

A

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

Any concordant results are then averaged.

18
Q

What colour is litmus in acid?

A

red

19
Q

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.

A

n = CV

n = 2M x 0.010 dm3 =0.02 mol

20
Q

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?

A

C = n/V

C = 0.02 / 0.020 = 1 mol/dm3 OR 1M

21
Q

Name the equipment below

A

A- volumetric flask

B- pipette

C- burette

22
Q

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

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

DO NOT FORGET - VOLUME MUST BE IN dm3

23
Q

What volume does 1 moles of ammonia gas occupy?

A

24 dm3

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

1 mole of any gas occupies 24dm3

24
Q

2H2 + O2 ⇒ 2H2O

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

A

2H2 + 1O2 ⇒ 2H2O

40dm3 of hydrogen

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

Mole ratio of O2 : H2 is 1 : 2

25
Q

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

A

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

26
Q

Rearrange the concentration equation in term of volume

A

V = n / C

27
Q

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

A

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.

28
Q

What volume does 2 moles of argon gas occupy?

A

48 dm3

V = n x molar volume = 2 mol x 24dm3/mol = 48dm3

1 mole of any gas occupies 24dm3

29
Q

What colour is phenolphthalein in alkali?

A

pink

30
Q

2H2 + O2 ⇒ 2H2O

What volume of water vapour is produced from 70 dm3 of hydrogen?

A

2H2 + O2 ⇒ 2H2O

70dm3 of water vapour

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

Mole ratio of H2 : H2O is 2 : 2

31
Q

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

A

1000cm3 = 1 dm3

10 dm3

32
Q

How do you get a burette ready for titration?

A
  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
33
Q

What is molar volume

A

Molar volume is the volume of one mole of gas at room temperature

Molar volume = 24 dm3 / mol

34
Q

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

A

repeating makes the results more reliable

reliable = repeatable

35
Q

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

A

1 mole of hydrogen molecules

1 mole of any gas occupies 24dm3 at room temp

36
Q

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

A

moles = volume / molar volume

37
Q

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

A
38
Q

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?

A

Use mole ratio

NaOH : HCl

1 : 1

Therefore, 0.02 moles of sodium hydroxide reacted

39
Q

Why is an indicator needed during titration?

A

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.

40
Q

What colour is phenolphthalein in acid?

A

colourless

RGS 5th Form Chemistry CH-F (10 decks)

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