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2 years ago

Explain how melting is considered endothermic

Chemistry

1 answer:

Eddi Din [679]2 years ago

4 0

Melting is a process involving absorption of energy which means that it is endothermic.

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Suppose the half-life is 9.0 s for a first order reaction and the reactant concentration is 0.0741 M 50.7 s after the reaction s

bazaltina [42]

Answer: The time taken by the reaction is 84.5 seconds

Explanation:

The equation used to calculate half life for first order kinetics:

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

where,

$t_{1/2}$ = half-life of the reaction = 9.0 s

k = rate constant = ?

Putting values in above equation, we get:

$k=\frac{0.693}{9}=0.077s^{-1}$

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

$k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}$ ......(1)

where,

k = rate constant = $0.077s^{-1}$

t = time taken for decay process = 50.7 sec

$[A_o]$ = initial amount of the reactant = ?

[A] = amount left after decay process = 0.0741 M

Putting values in equation 1, we get:

$0.077=\frac{2.303}{50.7}\log\frac{[A_o]}{0.0741}$

$[A_o]=3.67M$

Now, calculating the time taken by using equation 1:

$[A]=0.0055M$

$k=0.077s^{-1}$

$[A_o]=3.67M$

Putting values in equation 1, we get:

$0.077=\frac{2.303}{t}\log\frac{3.67}{0.0055}\\\\t=84.5s$

Hence, the time taken by the reaction is 84.5 seconds

6 0

3 years ago

The fifth element in group 7 in astatine would you expect it to be gas, liquid, or solid? why?

Ymorist [56]

Answer:

solid

Explanation:

Melting and boiling points of Group 7 elements State at room temperature Room temperature is usually taken as being 25°C. At this temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. There is therefore a trend in state from gas to liquid to solid as you go down the group.

6 0

1 year ago

Which change occurs when an atom in excited state returns to ground state? 1 energy is emitted 2energy is absorbed 3 the number

kozerog [31]

The answer is number 1 - energy is emitted

Energy is released when an atom in an excited state returns to the ground state.

7 0

2 years ago

Read 2 more answers

a teacher uses a bow and arrow to demonstrate accuracy and precision. she shoots several arrows, aiming at the exact center of t

Vera_Pavlovna [14]

A teacher uses a bow and arrow to demonstrate accuracy and precision. she shoots several arrows, aiming at the exact center of the target each time. thedrawing below shows where her arrows hit the target.
 The statement that best describes her shots is
Her shots were neither accurate nor precise
hope it helps

7 0

3 years ago

A ring costs $36 more than a bracelet. the cost of the bracelet is 4/7 the cost of the ring. find the total of the two items.

avanturin [10]

So let's use some equations to represent the data [let R= cost of ring & B= cost of bracelet]

R= B + $ 36 .... (1)

B= $\frac{4}{7}$ × R ... (2)

By using simultaneous equations to solve for B and R.
Substitute eq. (1) into eq. (2)

B = $\frac{4}{7}$ × (B + $36)

B = $\frac{4}{7}$ B + $\frac{144}{7}$

$( \frac{7}{7} - \frac{4}{7} ) B = \frac{144}{7}$

$\frac{3}{7} B = \frac{144}{7}$

⇒ B = $48

By substituting value of B into ea (1)

If R = B + $36

R = ($48) + $36

= $84

∴ the total of the two items = R + B
= $84 + $48
 = $132

7 0

3 years ago