The answer is The student forgot to add phenolphthalein.
Phenolphthalein<span> is a </span>chemical compound<span> with the </span>formula C20H14O4<span> and is often written as "</span>HIn" or "phph<span>" in shorthand notation. Phenolphthalein is often used as an indicator in </span>acid–base titrations<span>. For this application, it turns colorless in </span>acidic<span> solutions and pink in </span>basic <span>solutions.</span>
The enthalpy change for the formation step of this intermediate is 136 kJ/mol.
<h3>What is the enthalpy?</h3>
The enthalpy of reaction can be obtained from the enthalpies of formation of the species involved. The enthalpy of reaction is the heat evolved or absorbed in a reaction.
Thus, the enthalpy change for the formation step of this intermediate is 4 * 34 kJ/mol = 136 kJ/mol.
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The total area that could be covered by this roll of tape is 0.1524 m².
<h3>What is the double-sided tape?</h3>
A double-sided tape is a tape that can be stick from both sides. It is used to stick something on a surface. A rectangle is an object that has four sides in which two sides are equal.
If we unroll the tape, we will see that it is a rectangle with dimensions:
length = 6.35 m
width = 1.2 x 10⁻² m
Since the tape has two sides, the total area of the tape is:
A = 2 x (length x width)
A = 2 x 6.35 x 1.2 x 10⁻²
A = 0.1524 m²
Thus, the total area of the tape is 0.1524 m²
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To
determine the empirical formula of the compound given, we need to determine the ratio of each element in the compound. To do that we assume to have 100 grams sample
of the compound with the given composition. Then, we calculate for the number
of moles of each element. We do as follows:<span>
mass moles
C 56.79 4.73
H 6.56 6.50
O 28.37 1.77
N 8.28 0.59
Dividing the number of moles of each element with
the smallest value, we will have the empirical formula:
</span> moles ratio
C 4.73 / 0.59 8
H 6.50 / 0.59 11
O 1.77 / 0.59 3
N 0.59 / 0.59 1<span>
</span><span>
The empirical formula would be C8H11O3N.</span>
