C3.4 Acids, ions, and metals Flashcards

1
Q

What can a flame test be used for?

A

To detect the presence of a metal ion in a compound

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2
Q

How do you complete a flame test?

A

Dip a clean loop in the sample solution
Hold the flame test in the bunsen burner flame
Observe the colour of the flame

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3
Q

How do you test for positive ions ( cations )

eg SODIUM bromide

A
  • Dissolve a small amount in water
  • Add sodium hydroxide solution
  • Identify the colour of the precipitate formed

If there is a WHITE precipitate, add MORE sodium hydroxide, If the precipitate does not dissolve, DO A FLAME TEST

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4
Q

What colour precipitate does iron II form

A

Green

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5
Q

What cation forms a red/brown precipitate?

A

Iron III

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6
Q

How can you identify copper?

A

Blue precipitate

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7
Q

What colour flames do Lithium, Magnesium, and Sodium produce?

A
Lithium = Red
Magnesium = No colour
Sodium = Yellow
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8
Q

Which cations would lilac or brick red flames indicate?

A

Lilac = potassium

Brick red = calcium

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9
Q

How do you test for negative ions (anions)?

A
  • Dissolve in water
  • Add Hydrochloric acid

If A gas is given off = CARBONATE
If no gas is given off ….

-Add hydrochloric acid + Barium chloride
If a white precipitate is formed = SULPHATE
OR
-Add nitric acid and silver nitrate to fresh solution
identify the colour precipitate formed

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10
Q

What ion is present when a white precipitate is formed?

A

CHLORIDE

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11
Q

How do you identify a BROMIDE ion

A

Forms a CREAM precipitate with nitric acid and silver nitrate

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12
Q

What ion is present when a YELLOW precipitate is formed?

A

IODIDE

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13
Q

How are titrations used to identify the acidity of a solution?

A

Titrations can be used to determine the volume of acid and alkali needed to react together to produce a neutral solution

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14
Q

25 cm3 of dilute hydrochloric acid is neutralised by 20 cm3 of 0.5 mol/dm3 sodium hydroxide. What is the concentration of the hydrochloric acid?

A

-Convert volumes to dm3
-Determine the number of moles of sodium hydroxide
(moles of NaOH = concentration × volume)
-Work out the number of moles of acid using the balanced equation
- Calculate the concentration of the acid
(concentration of HCl = number of moles ÷ volume)

Ans = 0.4mol/dm3

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