Potassium ......................
Answer:

Explanation:
We need to use the formula for heat of vaporization.

Identify the variables.
- The heat absorbed by the evaporating water is the <u>latent heat of vaporization. </u>For water, that is 2260 Joules per gram.
- Q is the energy, in this problem, 50,000 Joules.
- m is the mass, which is unknown.

Substitute the values into the formula.

We want to find the mass. We must isolate the variable, m.
m is being multiplied by 2260 J/g. The inverse operation of multiplication is division. Divide both sides by 2260 J/g.


Divide. Note that the Joules (J) will cancel each other out.


Round to the nearest whole number. The 1 in the tenth place tells us to leave the number as is.

The mass is about 22 grams, so choice B is correct.
For very large numbers, it is much more convenient to use scientific notation. To do this, detect first the position of the decimal point. For whole numbers, the decimal point is place implicitly after the very last digit. Then, move this decimal point to the left until you reach to the last digit. In this case, you moved 8 places until you reach 6.4. Because the number is more than 1, the exponent would have a positive sign. Hence, the scientific notation would be 6.4×10⁸.
Answer: True
Explanation: For example, changing direction can change velocity
The answer for the following problem is mentioned below.
- <u><em>Therefore the final moles of the gas is 14.2 × </em></u>
<u><em> moles.</em></u>
Explanation:
Given:
Initial volume (
) = 230 ml
Final volume (
) = 860 ml
Initial moles (
) = 3.8 ×
moles
To find:
Final moles (
)
We know;
According to the ideal gas equation;
P × V = n × R × T
where;
P represents the pressure of the gas
V represents the volume of the gas
n represents the no of the moles of the gas
R represents the universal gas constant
T represents the temperature of the gas
So;
V ∝ n
= 
where,
(
) represents the initial volume of the gas
(
) represents the final volume of the gas
(
) represents the initial moles of the gas
(
) represents the final moles of the gas
Substituting the above values;
= 
= 14.2 ×
moles
<u><em>Therefore the final moles of the gas is 14.2 × </em></u>
<u><em> moles.</em></u>