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Molecular weight is an important concept in chemistry that tells us the mass of a single molecule of a substance. It is expressed as grams per mole (g/mol). To find molecular weight, we divide the mass of the sample by the number of moles. For example, when you know a sample weighs 2.30 grams and contains 0.0136 moles, calculating the molecular weight is straightforward.
Using the formula \( \text{Molecular Weight} = \frac{\text{Mass}}{\text{Moles}} \), you simply divide the mass by the number of moles. This helps us understand how much one mole of the solid would weigh.
In practical terms, knowing the molecular weight allows chemists to measure out exact quantities of substances for reactions.

Pressure conversion is necessary when dealing with different units that measure pressure. In this problem, we start with mmHg (millimeters of mercury) and need to convert to atmospheres (atm). One atmosphere is defined as 760 mmHg.
To convert mmHg to atm, use the formula:

• \( \text{Pressure in atm} = \frac{\text{Pressure in mmHg}}{760} \)

So for a pressure of 985 mmHg, the conversion results in approximately 1.296 atm.
This conversion is crucial because the ideal gas law often uses atmosphere as the standard unit for pressure. Accurate conversion ensures the correct application of the gas laws.

Temperature in gas calculations must often be in Kelvin, a unit that begins at absolute zero. The Kelvin scale is necessary because it ensures that temperatures are always positive, avoiding negative values that can disrupt calculations.
To convert from Celsius to Kelvin, add 273.15 to the Celsius temperature:

• \( T(\text{K}) = T(\text{°C}) + 273.15 \)

For example, 148°C becomes 421.15 K.
Using Kelvin in the ideal gas law \( PV = nRT \), the temperature variable must be in this unit so that the gas constant \( R \) used in calculations matches with pressure in atmospheres and volume in liters.

Volume conversion is an essential step when working with gases and the ideal gas law. Here, the volume is given in milliliters, but needs to be converted to liters because the gas constant \( R \) in the ideal gas law uses liters.
The conversion is simple:

• 1 liter = 1000 milliliters

Given a volume like 345 mL, convert it to liters by dividing by 1000:

• \( V(\text{L}) = \frac{345 \text{ mL}}{1000} = 0.345 \text{ L} \)

Using liters in calculations ensures consistency with the units of pressure and temperature, allowing for accurate application of the ideal gas law.