Which element should remain constant if Charles's law is applied to a gas sample?

Here are the solutions to the questions:

14. Which element should remain constant if Charles's law is applied to a gas sample?
Charles's Law states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature. Therefore, pressure and the number of moles (amount of gas) must remain constant.
The correct option is B.
B. Pressure and the number of moles of a gas

15. What is the value of the gas constant R?
The universal gas constant R has a standard value of $8.314 \text{ J mol}^{-1} \text{ K}^{-1}$.
The correct option is A.
A. $8.314 \text{ J mol}^{-1} \text{ K}^{-1}$

16. According to Charles's law, if the temperature of a gas at constant pressure is increased, the volume will also
Charles's Law states that $V \propto T$ (at constant pressure and number of moles). This means that volume and temperature are directly proportional. If the temperature increases, the volume will also increase.
The correct option is A.
A. Increase

17. Which of the following statements is false?
Let's analyze each statement:

• A. At constant temperature, Charles' law applies - Charles's law applies at constant pressure, not constant temperature. This statement is false.
• B. The pressure of a given mass of gas decreases as the volume is increased at constant temperature - This describes Boyle's Law, which is true.
• C. Isobaric changes are those which occur at constant pressure - "Isobaric" means constant pressure. This statement is true.
• D. Boyle's law applies at constant temperature - This is the definition of Boyle's Law. This statement is true. The false statement is A. A. At constant temperature, Charles' law applies

18. For a gas, which pair of variables are inversely proportional to each other (if all other conditions remain constant)?
According to the ideal gas law ($PV = nRT$), if the number of moles ($n$) and temperature ($T$) are kept constant, then $PV = \text{constant}$. This means that pressure ($P$) and volume ($V$) are inversely proportional. This is Boyle's Law.
The correct option is B.
B. P, V

19. Bituminous is a common type of _____
Bituminous refers to bituminous coal, which is a type of coal.
The correct option is C.
C. coal

20. Wood Charcoal is an allotrope of _____
An allotrope is a different structural form of the same element. Charcoal, including wood charcoal, is primarily composed of carbon. Other allotropes of carbon include diamond and graphite.
The correct option is A.
A. carbon