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Chemistry AS level > 1.2 Amount Of Substance Part 1 > Flashcards

1.2 Amount Of Substance Part 1 Flashcards

1
Q

Define relative atomic mass (Ar)

A

The weighted average of all the isotopes relative to 1/12th the mass of carbon-12

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2
Q

How do you calculate the Ar? (Relative atomic mass)

A

(Mass x abundance of each isotope) / total abundance

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3
Q

Define the relative molecular mass

A

The mass of a molecule of the compound relative to 1/12th of the mass of an atom of carbon 12

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4
Q

Define relative formula mass

A

The mass of one formula unit of an ionic compound relative to 1/12th of the mass of an atom of carbon-12

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5
Q

Define a mole

A

The amount of substance that contains as many particles as there are in exactly 12g of carbon-12

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6
Q

The mass of one mole of a substance is equal to what?

A

Its Mr in grams

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7
Q

What is molar mass measured in?

A

gmol-1

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8
Q

How many mole equations are there?

A

4

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9
Q

What is the first mole equation

A

Mol = mass (g) / Mr

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10
Q

What is the second mole equation?

A

Mol = concentration (moldm-3) x volume (dm3)

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11
Q

What is the 3rd mole calculation?

A

Mol = number of particles / Avogadro’s constant

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12
Q

What is the fourth mole equation?

A

Mol = P(Pa)xV(m3) / R(8.314)xT(K)

P= pressure 
V= volume 
T= temp
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13
Q

Calculate the number of moles in 36g of water

A

2.0 (mass/mr)

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14
Q

Calculate the mass of 5 moles of methane

A

80g (MrxMol)

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15
Q

Calculate the number of moles in 50 mg of iodine

A

2.0 x10(-4) (mass/mr)

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16
Q

Calculate the number of moles of ammonia in 34kg

A

2000mol (mass/Mr)

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17
Q

Calculate the number of moles of calcium carbonate in 2 tonnes

A

20000mol (mass/Mr)

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18
Q

Calculate the number of carbon atoms in 100mg of diamond

A

5.02 x10(2)

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19
Q

How many grams of magnesium contains 1.204 x10(24) atoms?

A

48.6g

20
Q

How do you convert cm3 to dm3?

A

x10(-3)

21
Q

How do you convert from dm3 to cm3?

A

x10(3)

22
Q

Calculate the number of moles hydrochloric acid in 25.0 cm3 of a 0.200 moldm(-3) solution

A

5.00 x10(-3)

23
Q

Calculate the volume of 0.050 moldm(-3) NaOH which contains 0.020 moles

A

0.40 dm3

24
Q

When doing mole calculation what MUST mass be in?

A

grams

25
Q

When doing mole calculations what MUST volume be in?

A

dm3

26
Q

Calculate the mass of sodium chloride required to make 50cm3 of a 0.25 moldm(-3) solution

A

0.73g

27
Q

8.00g of NaOH is dissolved in 250cm(3) of solution. Calculate its concentration in moldm(-3)

A

0.800 moldm(-3)

28
Q

What are the assumptions made for the ideal gas equation?

A
  • There are no intermolecular forces between the molecules

* The volume occupied by the molecules themselves is entirely negligible relative to the volume of the container

29
Q

Convert 25 degrees to kelvin

A

298K

30
Q

Convert -40 degrees to Kelvin

A

233K

31
Q

How do you change degrees to kelvin?

A

Add on 273

32
Q

What volume, in cm3, is occupied by 0.25mol of a gas at a pressure of 150 kPa and a temperature of 20 degrees Celsius?

A

4.1 x103 (ideal gas equation)

33
Q

At 450K an 800mg sample of helium occupies a glass bulb of volume in 10.0dm3. Calculate the pressure, in kPa, exerted by the helium under these conditions

A

74.8 kPa (ideal gas equation)

34
Q

0.7100g of a gas when contained in a vessel of volume 8.200 x 102 cm3 exerted a pressure of 50.65 kPa at a temperature of 227.0degrees Celsius. Calculate the moles and then the Mr of the gas. Suggest it’s identity.

A

Mr - 71.06

Cl2

35
Q

What is the unit for density (chemistry)

A

gcm(-3)

36
Q

50 cm3 of ethanol has a mass of 38g. Calculate its density.

A

0.76 gcm(-3)

37
Q

There are 550mol of pure platinum in a bar measuring 10cm by 10cm by 50cm. What is the density of platinum in kgdm(-3)

A

21kgdm(-3)

38
Q

A sample of sodium chloride, density 2.16 gcm(-3), has a volume of 5 x 10(-2) cm3. Calculate the number of ions in the sample.

A

3.69 x(-3)

39
Q

Define empirical formula

A

The simplest whole number ratio of atoms of each element present in a molecule

40
Q

Define molecular formula

A

The actual number of atoms of each element present in a molecule

41
Q

Find the empirical formula of an oxide of sulfur formed when 3.2g sulfur combines with 3.2g of oxygen

A

SO2

42
Q

How do you calculate empirical formula?

A
  • Work out the number of moles

* Divide by the smallest number

43
Q

Find the empirical formula of phosphorus formed when 1.24g phosphorus combines with 0.96 of oxygen.

A

P2O3

44
Q

Find the empirical formula of an oxide of lead formed when 6.2g lead burns in oxygen to give 6.84g of the oxide

A

Pb3O4

45
Q

Find the empirical formula of s compound containing the following percentages mass:
Na- 32.4%
S- 22.5%
O- 45.1%

A

Na2SO4

46
Q

What do you need to calculate the molecular formula?

A
  • the empirical formula

* the Mr

47
Q

A compound of Mr 188 has the following percentage composition by mass:
C 12.78%, H 2.13%, Br 85.2%

Calculate the molecular formula

A

Empirical - CH2Br

Molecular - C2H4Br2

Chemistry AS level (8 decks)

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