8519895
Descripción
Test por Kate Blowers, actualizado hace más de 1 año
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Creado por Kate Blowers
hace alrededor de 7 años
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Pregunta 1
Pregunta
What is the correct equation for working out the percentage mass of an element in a compound?
Respuesta
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(Relative formula mass x number of atoms of that element)/relative atomic mass of compound
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(Relative atomic mass x number of atoms of that element)/relative formula mass of compound
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(Relative atomic mass x relative formula mass of compoun)/number of atoms of that element
Pregunta 2
Pregunta
A mole is a system chemists use to count huge quantities of [blank_start]atoms or molecules[blank_end]. It is given the symbol [blank_start]n[blank_end], and is measured in a unit called the mole, shorthand [blank_start]mol[blank_end]. A mole of any substance contains the same number of atoms that are contained in [blank_start]12[blank_end]g of the isotope [blank_start]carbon-12[blank_end]. One mole of a substance is simply the [blank_start]relative atomic mass[blank_end] or [blank_start]formula mass[blank_end] expressed in [blank_start]grams.[blank_end]
Respuesta
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atoms or molecules
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n
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mol
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12
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carbon-12
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relative atomic mass
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formula mass
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grams.
Pregunta 3
Pregunta
The reactant that gets used up first in a reaction is called the limiting reactant
Respuesta
- True
- False
Pregunta 4
Pregunta
Which of these do you need to work out the limiting reactant?
Respuesta
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A balanced symbol equation
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The relative formula mass
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The number of moles of each reactant
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The number of electrons
Pregunta 5
Pregunta
Percentage yield is the amount of a produce you [blank_start]actually make[blank_end] as a [blank_start]percentage of the amount[blank_end] you should [blank_start]theoretically make.[blank_end]
Respuesta
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actually make
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percentage of the amount
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theoretically make
Pregunta 6
Pregunta
Why does a high percentage yield matter to people in the industry?
Respuesta
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If a yield is know for a particular product you can work out how much reactant is needed
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A higher percentage yield = less product to produce more = higher profit
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It's easier to work out information
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Raw materials are scarce and expensive and so must be carefully conserved
Pregunta 7
Pregunta
What is the correction equation for working out percentage yield?
Respuesta
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Percentage yield = (Theoretical yield/actual yield) x 100
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Percentage yield = (Number of atoms/theoretical yield) x 100
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Percentage yield = (Actual yield/theoretical yield) x 100
Pregunta 8
Pregunta
Very few reactants have a percentage yield of 100% because:
Respuesta
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Products may be left behind in the apparatus
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It violates the law of conservation of mass
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The reaction may not have completely finished
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The raw minerals may not be pure
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The atoms are destroyed in the reaction
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Some reactants may give unexpected products
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