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lisov135 [29]
3 years ago
5

To standardize a hydrochloric acid solution, it was used as a titrant with a solid sample of sodium hydrogen carbonate, NaHCO3.

The solid sample had a mass of 0.3967g, and 41.77 mL of acid was required to reach the equivalence point. Calculate the concentration of the standard solution.
Chemistry
1 answer:
Ket [755]3 years ago
6 0

Answer:

0.113 M

Explanation:

The reaction that takes place is:

  • NaHCO₃ + HCl →NaCl + CO₂ + H₂O

First we convert 0.3967 g of NaHCO₃ into moles, using its molar mass:

  • 0.3967 g ÷ 84 g/mol = 4.72x10⁻³ mol NaHCO₃

As 1 mol of NaHCO₃ reacts with 1 mol of HCl, in 41.77 mL of the HCl solution there were 4.72x10⁻³ moles of HCl.

With the <em>calculated number of moles and the given volume </em>we <u>calculate the concentration of the solution</u>:

  • Converting 41.77 mL ⇒ 41.77 mL / 1000 = 0.04177 L
  • Concentration = 4.72x10⁻³ mol / 0.04177 L = 0.113 M
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<em>The correct option is A) The atom has changed over the years.</em>

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Option A is not correct because an atom does not change. It remains the same always. The structure of an atom will always contain neutrons, protons and electrons.

Scientific theories tend to change over time as new information is brought up. Novel techniques lead to more advanced experiments and results. As a result, a scientific theory is subjected to change whenever evidence is found for a new theory which challenges the older one.

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Answer: The given statement is true.

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If there is shortage of water then its prices will go high and hence we need to pay more for it.

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Which two particles are found in the center of an atom?
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7. The equilibrium constant Kc for the reaction H2(g) + I2(g) ⇌ 2 HI(g) is 54.3 at 430°C. At the start of the reaction there are
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Answer:

[H2] = 0.0692 M

[I2] = 0.182 M

[HI] =  0.826 M

Explanation:

Step 1: Data given

Kc = 54.3 at 430 °C

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Volume = 2.40 L

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H2 + I2 → 2HI

Step 3: Calculate Q

If we know Q, we know in what direction the reaction will go

Q = [HI]² / [I2][H2]

Q= [n(HI) / V]² /[n(H2)/V][n(I2)/V]

Q =(n(HI)²) /(nH2 *nI2)

Q = 0.886²/(0.714*0.984)

Q =1.117

Q<Kc This means the reaction goes to the right (side of products)

Step 2: Calculate moles at equilibrium

For 1 mol H2 we need 1 mol I2 to produce 2 moles of HI

Moles H2 = 0.714 - X

Moles I2 = 0.984 -X

Moles HI = 0.886 + 2X

Step 3: Define Kc

Kc = [HI]² / [I2][H2]

Kc = [n(HI) / V]² /[n(H2)/V][n(I2)/V]

Kc =(n(HI)²) /(nH2 *nI2)

KC = 54.3 = (0.886+2X)² /((0.714 - X)*(0.984 -X))

X = 0.548

Step 4: Calculate concentrations at the equilibrium

[H2] = (0.714-0.548) / 2.40 = 0.0692 M

[I2] = (0.984 - 0.548) / 2.40 = 0.182 M

[HI] = (0.886+2*0.548) /2.40 = 0.826 M

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