Which type of material incorporates a variety of substances to enhance desired properties such as strength and flexibility?

Which of the following item(s) explain the differences between the Ka values. Choose one or more: A. The oxidation state for oxy

Allisa [31]

Answer:

C. The electron-withdrawing fluorine atoms pull electron density from the oxygen in trifluoroacetate. The negative charge is more stabilized in trifluoroacetate by this effect.

Explanation:

The structures of trifluoroacetate and acetic acid are both shown in the image attached.

The trifluoroacetate anion (CF3CO2-), just like the acetate anion has in the middle, two oxygen atoms.

However, in the trifluoroacetate anion, there are also three electronegative fluorine atoms attached to the nearby carbon atom attached to the carbonyl, and these pull some electron density through the sigma bonding network away from the oxygen atoms, thereby spreading out the negative charge further. This effect, called the "inductive effect" stabilizes the anion formed,the trifouoroacetate anion is thus more stabilized than the acetate anion.

Hence, trifluoroacetic acid is a stronger acid than acetic acid, having a pKa of -0.18.

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3 0

3 years ago

Cobalt-60 is a strong gamma emitter that has a half- life of 5.26 yr. The co balt-60 in a radiotherapy unit must be replaced whe

Alenkasestr [34]

Answer: The sample of Cobalt-60 isotope must be replaced in January 2027

Explanation:

The equation used to calculate rate constant from given half life for first order kinetics:

$t_{1/2}=\frac{0.693}{k}$

where,

$t_{1/2}$ = half life of the reaction = 5.26 years

Putting values in above equation, we get:

$k=\frac{0.693}{5.26yrs}=0.132yrs^{-1}$

Rate law expression for first order kinetics is given by the equation:

$k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}$

where,

k = rate constant = $0.132yr^{-1}$

t = time taken for decay process = ? yr

$[A_o]$ = initial amount of the sample = 100 grams

[A] = amount left after decay process = (100 - 75) = 25 grams

Putting values in above equation, we get:

$0.132=\frac{2.303}{t}\log\frac{100}{25}\\\\t=10.5yrs$

The original sample was purchased in June 2016

As, June is the 6th month of the year, which means the time period will be $2016+\frac{6}{12}=2016.5$

Adding the time in the original time period, we get:

$2016.5+10.5=2027$

Hence, the sample of Cobalt-60 isotope must be replaced in January 2027

3 0

3 years ago

How many moles of Kl are needed to make 4.07 L of a 1.138 M solution?

Nata [24]

Answer:

A

Explanation:

cause

5 0

3 years ago

Chemical reactions can be detected by precipitation of a _____ from a solution.

RideAnS [48]

Answer: solid

Explanation: Chemical reactions are those which involve rearrangement of atoms.

Chemical changes are accompanied by following changes:

1) Absorption or release of heat

2) Change in color

3) Formation of gas bubbles

4) Formation of a solid product called as precipitate

Example of formation of precipitate or solid in chemical reaction: $2AgNO_3(aq)+BaCl_2(aq)\rightarrow 2AgCl(s)+Ba(NO_3)_2(aq)$

7 0

3 years ago

Read 2 more answers

How does a molecule differ from an atom?

Eddi Din [679]

Answer:

According to my research A molecule is two or more atoms held together by covalent bonds. An atom is the smallest part of an element. ... A sodium atom has one outer electron, and a carbon atom has four outer electrons.

Explanation:

5 0

3 years ago