Quantitative Chemistry Flashcards

1
Q

What is the law of conservation of mass

A

No atoms are lost or made during a chemical reaction so the mass of the products equal the mass of the reactants

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2
Q

Where are the products and reactants

A

Reactants left products right

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3
Q

92g of sodium reacts with 32g of oxygen, calculate the mass of sodium oxide produced

A

92 + 32 = 124g because the mass of the product is equal to the mass of the reactants and no atoms can be lost or made in a chemical reaction

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4
Q

How do you work out uncertainty from sets of repeated measurements

A

Range of values
———————-
2

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5
Q

How to workout range

A

Maximum value - minimum value

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6
Q

What do group 1 metals, group 2 metals, group 6 non metals and group 7 non metals form?

A
  • group one metals form +1 ions
  • group two metals form +2 ions
  • group six non metals form -2 ions
  • group seven non metals form -1 ions
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7
Q

How to work out uncertainty using a scale such as a ruler

A

The uncertainty in the measurement is half of the smallest division

It would be expressed as

6.4 (biggest measurement on shape measured) -+ (minus on bottom) 0.05 (half of the smallest division)

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8
Q

What is the uncertainty using a digital device

A

The smallest digit on the device would be the uncertainty

The uncertainty would be the weight of whatever u were weighing +- the smallest digit on the scale

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9
Q

What are the two types of error

A
  • random error

- systematic error

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10
Q

What is the error

A

The difference between the measured value and the true value

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11
Q

What is random error

A

An error caused by factors that vary between readings (eg reaction time)

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12
Q

How to calculate number of moles in elements

A

Number of moles = Mass (g)
——————————
Relative atomic mass Ar

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13
Q

How to calculate number of moles in compounds

A

Number of moles = Mass (g)
——————————
Relative formula mass Mr

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14
Q

You are given 120g of calcium, how many moles have you been given? Ar for calcium = 40

A

120
—— = 3 moles
40

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15
Q

What does abundance mean

A

How common an isotope is

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16
Q

Key facts about relative formula mass

A
  • no units

- never involves big numbers such as 2CH

17
Q

What is relative formula mass

A

The relative atomic masses added together

18
Q

You are given a sample of calcium carbonate (CACO3) with a mass of 300g. Calculate the number of moles of calcium carbonate in the sample.
Ar Ca= 40 Ar C= 12 ArO= 16

A

40 + 12 + (16 x 3) = relative formula mass
= 100

300
——- = 3 moles
100

19
Q

How to calculate mass (in terms of moles)

A

Mass (g) = number of moles x relative formula mass Mr

20
Q

What does it mean if there is no big number

A

It’s a one (like 1 MG)

21
Q

What do you have to have in order to calculate masses or products (amounts of substances in reactions

A

Balanced formula equations

22
Q

What are molecules in an equation

A

The big number

23
Q

What is the formula mass

A

The masses of each element x by the number of molecules etc

eg. 2H(small 2)O 1 H x 4 = 4 16 O x 2 = 32 32+4=36

24
Q

Calculate the mass of magnesium chloride thay could be produced from 72g of magnesium. Assume that the chlorine is unlimited. Ar Mg = 24. Ar CI = 35.5

A

Mg + CI(small 2) ———-> MgCI(small 2)

No of moles= 72
—— = 3 moles (Mg) —> 3 moles (MgCI)
24

Mass = 3 x 95 (relative formula mass of MgCI) = 285g

25
Q

What is avogadros constant

A

1 mole which is 6.02 x 10 to the power of 23

26
Q

Calculate the number of moles of atoms in one mole of calcium hydroxide Ca(OH)2

A

Ca = 1 atom (OH)2 = 4 atoms

4+1=5

1 mole of calcium hydroxide molecules contains 5 moles of atoms

27
Q

What is the limiting reactant

A

The reactant that is fully used up

28
Q

What is the excess reactant

A

The reactant that isn’t used up

29
Q

What is meant by concentration (concentration of solution) and what is the unit

A
  • tells us the mass of a solute in a given volume of solution
  • g/dm cubed
30
Q

What is a solute

A

A chemical dissolved in a solvent (water is often used as a solvent

31
Q

What is the calculation for concentration

A

Concentration (g/dm cubed) = Mass (g)
—————-
Volume (dm cubed)

  • mass is at the top of the triangle
32
Q

How does the mass of a solute and the mass of a solution affect the concentration

A
  • if we increase the mass of solute and keep the volume the same, then we increase the concentration
  • if we increase the volume of solution and keep the mass of the solute the same, then we decrease the concentration