The indicator methyl red has different molecular structures at high and low pH.

Chemistry

1 answer:

Novosadov [1.4K]2 years ago

6 0

Answer:

a. True

Explanation:

Methyl red is an indicator widely used in quality control of oxides as Zinc oxide in the titration with sulfuric acid.

As is used in titrations of acid-base reactions the indicator change in colour. Is red when the pH < 4.4 (Acidic Solutions) and is yellow when pH > 6.2 (Neutral-Basic solutions).

A change in colour means the structure of the indicator is changing with pH. Thus, the answer is:

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Determine the molecular formulas of these compounds:

lianna [129]

The molecular formulas of the empirical ones of P₂O₅ and CH₂O are P₄O₁₀ and C₇H₁₄O₇, respectively, knowing that their molar masses are 310 and 200.18 g/mol, respectively.

<h3>1. Molecular formula of P₂O₅</h3>

We can calculate the molecular formula as follows:

$MF = n*EF$ (1)

Where:

MF: is the molecular formula

EF: is the empirical formula

n: is an integer

To calculate the integer <em>n</em>, we need to use the following equation:

$n = \frac{M}{M_{EF}}$ (2)

Where:

M: is the molar mass of P₂O₅ = 310 g/mol

$M_{EF}$ : is the molar mass of the empirical formula

The molar mass of the empirical formula of P₂O₅ is given by:

$M_{EF} = 2A_{P} + 5A_{O}$

Where:

$A_{P}$ : is the atomic weight of phosphorus = 30.974 g/mol

$A_{O}$ : is the <em>atomic weight</em> of oxygen = 15.999 g/mol

So, the <em>molar mass</em> of the <em>empirical formula</em> of P₂O₅ is:

$M_{EF} = (2*30.974 + 5*15.999) g/mol = 141.943 g/mol$

Now, we can find the integer <em>n </em>(eq 2).

$n = \frac{M}{M_{EF}} = \frac{310 \:g/mol}{141.943 \:g/mol} = 2$

Finally, after multiplying the integer <em>n</em> by the number of atoms on the empirical formula of P₂O₅, we have (eq 1):

$MF = n*EF = 2 \times P_{2}O_{5} = P_{(2 \times 2)}O_{(5 \times 2)} = P_{4}O_{10}$

Therefore, the molecular mass of P₂O₅ is P₄O₁₀.

<h3>2. Molecular formula of CH₂O </h3>

We know:

M: molar mass of CH₂O = 200.18 g/mol

To calculate the integer <em>n</em> and so the molecular mass of the molecule, we need to calculate the<em> molar mass</em> of the <em>empirical formula</em> of CH₂O.

$M_{EF} = A_{C} + 2A_{H} + A_{O} = (12.011 + 2*1.008 + 15.999) g/mol = 30.026 \:g/mol$