A physical change is ...

Chapter 5. You must show all your work. Solve the following problems. (a) (8 points) When a cold drink is taken from a refrigera

GuDViN [60]

Answer:

see explanation below

Explanation:

To do this, we need to use the Newton's law of cooling which is:

dT/dt = (k - Ts)

Where:

Ts: temperature of surroundings (In this case, 20 °C)

k: constant

t: time

Now, after we do the integrals of this, the general expression would be:

T(t) = Ce^kt + Ts (1)

Now, with the first data, we need to calculate the value of C. This value will be the same after time has passed. You can see this as the concentration of the drink. As it's not experimenting any reaction, it's concentration remain the same, and only the temperature will change.

Now, to get the value of C, we can begin with the fact that at time = 0, temperature was 5°C so:

T(0) = Ce^k*0 + Ts

Replacing:

5 = Ce^1 + 20

5 - 20 = C*1

C = -15

Now that we have this, we can solve the first part of the problem

(i):

First, we need to get the value of k, we know the final temperature at t = 25, so we can solve for k, which is constant too, and then, calculate the temperature for t = 50 min

solving for k, with T = 10 °C, C = -15, Ts = 20 °C and t = 25 min:

10 = -15e^25k + 20

10 - 20 = -15e^25k

-10/-15 = e^25k

ln(-10/-15) = 25k

k = -0.405465/25

Now that we have k, let's calculate T after t = 50

T = -15e^(-0.0162)*50 + 20

T = -6.67 + 20

T(50) = 13.33 °C

(ii)

For this part, we only need to solve for t:

18 = -15e^(-0.0162)t + 20

18 - 20 / -15 = e^-0.0162t

0.1333 = e^-0.0162t

ln(0.1333) = -0.0162t

t = -2.0145/-0.0162

t = 124.37 min

8 0

3 years ago

In reading a line drawing, how do you know where atoms of these elements are in the structure if they are missing from the drawi

Tanya [424]

Answer:

The atoms of an element are represented in a chemical line drawing with its chemical formula.

Explanation:

chemical structural drawing helps to represent the pattern for which an element is formed. Chemical elements are made up of atoms that represent their single state.

The line drawing is made up of lines (representing the chemical bond between atoms) and the atoms or various atoms that make up the element.

7 0

3 years ago

A 3.0 L solution contains 73.5 g of H2SO4. Calculate the molar concentration of the solution.

kozerog [31]

$C_{m}=\frac{m}{MV}=\frac{73,5g}{98\frac{g}{mol}*3L}=0,25M\\\\
C_{1}V_{1}=C_{2}V_{2}\\\\
0,25M*3L=0,18M*V_{2}\\\\
V_{2}=\frac{0,25M*3L}{0,18M}\approx 4,17L\\\\
4,17L-3L=1,17L$

6 0

3 years ago

What are advantages of using uranium as an energy source

MariettaO [177]

Question:
What are advantages of using Uranium as an energy source?

Answer(s):
-Small amounts of Uranium generate large amounts of energy
-Uranium occurs in huge reserves
-It has a longer lifetime than other non-renewable sources of energy

-Brainly Answerer

4 0

4 years ago

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A student balances the following redox reaction using half-reactions.

ICE Princess25 [194]

Answer: 6.

Explanation:

1) Aluminum

$Al^0-3e^----\ \textgreater \ Al^{3+}$

So each atom of aluminum lost 3 electrons to pass from 0 oxidation state to 3+ oxidation state.

2) Manganesium

$Mn^{2+}+2e^{-}---\ \textgreater \ Mn$

So, each ion of Mn(2+) gained 2 electrons pass from 2+ oxidation state to 0.

3) Balance

Multiply aluminum half-reaction (oxidation) by 2 and multiply manganesium half-raction (reduction) by 3:

$2Al^{0}-6e^{-}---\ \textgreater \ 2Al^{3+}

3Mn^{2+}+6e^{-}---\ \textgreater \ 3Mn^{0}$

4) Net equation

Add the two half-equations:

$2Al^{0}+3Mn^{2+}----\ \textgreater \ 2Al^{3+}+3Mn^{0}$

As you see the left side has 2 Al, 3Mn, and 3*2 positive charges.

The right side has 2 Al, 3 Mn, and 2*3 positive charges.

So, the equation is balanced.

5) Count the number of electrons involved.

As you see 2 atoms of aluminum lost 6 electrons (3 each).

That is the answer to the question. 6 electrons will be lost.

5 0

3 years ago

Read 2 more answers