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ziro4ka [17]
3 years ago
5

WILL GIVE BRAINLYST

Chemistry
1 answer:
Andrew [12]3 years ago
3 0

Answer: 12.18 u

Explanation: The average atomic mass of an element is calculated by taking the weighted average of the atomic masses of its stable isotopes.

In other words, each stable isotope will contribute to the average mass of the element proportionally to its abundance.

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A. The half-life for a first order reaction in 49 minutes. What is the rate constant?B.For a second order reaction, the half-lif
Burka [1]

Answer:

a) 0,014 min⁻¹

b) 1452 seconds.

c) 0,02156 M

d) The faster rate is for the reaction A. The largest rate constant, k, is for A reaction

Explanation:

a) For a first order reaction the half-life is:

t_{1/2} = \frac{ln(2)}{k} <em>(1) </em>As half.life is 49 min. Rate constant -k- is: 0,014 min⁻¹

b) The half-life is defined as the time that takes in descompose the half of the initial concentration of a compound.

As half-life is 726s. In 726s the concentration will be 0,300M, In the next 726s the concentration will be 0,150M. Thus, thae time it takes to decrease concentration until 0,150M is 726s×2= 1452 seconds

c) In the same way, 11072 years are 4 half-life for this reaction, thus:

0,345M/2⁴ = 0,02156 M

d) By definition of half-life, the less half-life, the faster rate. Thus, The faster rate is for the reaction A.

By (1) half-life is inversely proportional to rate constant. Thus, the less half-life, the largest rate constant. The largest rate constant, k, is for A reaction

I hope it helps!

7 0
4 years ago
Which is of the following is the answer for reactions demonstrates a synthesis reaction?
andrew-mc [135]
The answer is D. This is because a synthesis reaction is when two elements combined to make a product (ex. A+B= AB). Hope this helps!
3 0
3 years ago
Determine whether or not the mixing of each of the two solutions indicated below will result in a buffer.
WARRIOR [948]
Part A

75.0 mL of 0.10 M HF; 55.0 mL of 0.15 M NaF

This combination will form a buffer.

Explanation

Here, weak acid HF and its conjugate base F- is available in the solution

Part B

150.0 mL of 0.10 M HF; 135.0 mL of 0.175 M HCl

This combination cannot form a buffer.

Explanation

Here, moles of HF = 0.15 x 0.1 = 0.015 moles

Moles of HCl = 0.135 x 0.175 = 0.023

Since HCl is a strong acid and the number of HCl is higher than HF. This prevents the dissociation of HF and the conjugate base F- will not be available in the solution

Part C

165.0 mL of 0.10 M HF; 135.0 mL of 0.050 M KOH

This combination will form a buffer.

Explanation

Moles of HF = 0.165 x 0.1 = 0.0165 moles

Moles of KOH = 0.135 x 0.05 = 0.00675 moles

Moles of KOH is not sufficient for the complete neutralization of HF. Thus weak acid HF and its conjugate base F- is available in the solution and form a buffer

Part D

125.0 mL of 0.15 M CH3NH2; 120.0 mL of 0.25 M CH3NH3Cl

This combination will form a buffer

Explanation

Here, weak acid CH3NH3+ and its conjugate base CH3NH2 is available in the solution and form a buffer

Part E

105.0 mL of 0.15 M CH3NH2; 95.0 mL of 0.10 M HCl

This combination will form a buffer

Explanation

Moles of CH3NH2 = 0.105 x 0.15 = 0.01575 moles

Moles of HCl = 0.095 x 0.1 = 0.0095 moles

Thus the HCl completely reacts with CH3NH2 and converts a part of the CH3NH2 to CH3NH3+. This results weak acid CH3NH3+ and its conjugate base CH3NH2 is in the solution and form a buffer
5 0
3 years ago
Which units describe the molarity of an aqueous sucrose solution? moles of sucrose per liter of solution grams of solution per l
r-ruslan [8.4K]
Molarity is one way of expressing concentration of solutions. It has units of moles of solute per liter of the solution. Take note, this is not only for sucrose solution, this is used for every solution. The correct answer from the choices is "moles of sucrose per liter of solution ".
7 0
3 years ago
Read 2 more answers
When a chemical reaction is at equilibrium, which of the following statements is always TRUE?
AysviL [449]

<u>Answer:</u> The correct answer is Option D.

<u>Explanation:</u>

Equilibrium constant is defined as the ratio of concentration of products to the concentration of reactants each raised to the power their stoichiometric coefficients. It is represented by K_{eq}

For a general chemical reaction:

aA+bB\rightarrow cC+dD

The K_{eq} is written as:

K_{eq}=\frac{[C]^c[D]^d}{[A]^a[B]^b}

There are 3 conditions:

  • When K_{eq}>1; the reaction is product favored.
  • When K_{eq}; the reaction is reactant favored.
  • When K_{eq}=1; the reaction is in equilibrium.

At equilibrium, the  ratio of concentration of reactants to the concentration of products is equal to 1.

At equilibrium, the rate of forward reaction is equal to rate of backward reaction.

Hence, the correct answer is Option D.

7 0
3 years ago
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