Question

Strictly speaking, the solvent is the component of a solution that is present in the largest amount on a mole basis. For solutions involving water, water is almost always the solvent because there tend to be many more water molecules present than molecules of any conceivable solute. To see why this is so, calculate the number of moles of water present in \(1.0 \mathrm{L}\) of water. Recall that the density of water is very nearly \(1.0 \mathrm{g} / \mathrm{mL}\) under most conditions.

Short answer

To find the number of moles of water in 1.0 L, first convert the volume to mass using the given density: 1.0 L = 1000 mL, so 1000 mL × 1.0 g/mL = 1000 g. Next, determine the molar mass of water (H2O): 2 × 1.008 g/mol (H) + 16.00 g/mol (O) = 18.016 g/mol. Finally, calculate the number of moles using the formula: Number of moles = Mass / Molar mass = (1000 g) / (18.016 g/mol) = 55.5 mol. Thus, there are 55.5 moles of water in 1.0 L of water.

Step-by-step solution

Convert volume to mass

We have the volume, 1.0 L, and we know that the density of water is 1.0 g/mL. First, we will convert the volume from liters to milliliters, then multiply by the density to find the mass of water. 1.0 L × 1000 mL/L = 1000 mL Next, calculate the mass of water using the density: 1000 mL × 1.0 g/mL = 1000 g

Determine the molar mass of water

We need to know the molar mass of water to convert from grams to moles. Water has the chemical formula H2O, so we can find its molar mass by adding the molar masses of two hydrogen atoms and one oxygen atom. Molar mass of hydrogen (H) = 1.008 g/mol Molar mass of oxygen (O) = 16.00 g/mol Molar mass of water (H2O) = 2 × Molar mass of H + Molar mass of O Molar mass of water (H2O) = 2 × 1.008 g/mol + 16.00 g/mol = 18.016 g/mol

Calculate the number of moles of water

Now that we have the mass of water (1000 g) and the molar mass of water (18.016 g/mol), we can use the following formula to find the number of moles: Number of moles = Mass / Molar mass Number of moles of water = (1000 g) / (18.016 g/mol) Number of moles of water = 55.5 mol Therefore, there are 55.5 moles of water in 1.0 L of water.

Key concepts

Understanding Solvent

When talking about solutions in chemistry, the solvent is the substance that is present in the largest amount. It dissolves other substances, which are known as solutes. The role of the solvent is crucial as it determines the state of the solution. In most aqueous solutions, water serves as the solvent. This is because water molecules are typically more abundant than any other molecules present. For example, in a solution where water is the solvent, there are more moles of water than moles of the solute. Therefore, understanding the nature and properties of the solvent is vital for comprehending how solutions work.

What is Molar Mass?

Molar mass is a fundamental concept in chemistry. It refers to the mass of one mole of a substance, measured in grams per mole (g/mol). To find the molar mass of a compound, you sum up the molar masses of its constituent elements. For instance, water (H₂O) has a molar mass derived from its atoms: 2 hydrogen atoms and 1 oxygen atom. The molar mass of each hydrogen atom is around 1.008 g/mol, while oxygen is approximately 16.00 g/mol.

Adding these gives us the molar mass of water:

• Molar mass of H₂O = 2 x 1.008 + 16.00 = 18.016 g/mol

Knowing the molar mass is crucial for converting between mass and moles, enabling precise calculations in chemical reactions.

Density of Water Explained

The density of a substance is its mass per unit volume. For water, the density is commonly accepted as 1.0 g/mL under normal conditions. This means that 1 milliliter of water weighs 1 gram.

Understanding the density of water allows us to easily convert between the volume and mass of water. For instance, if you have 1 liter of water, you can effortlessly convert this volume to mass because:

• 1 L of water = 1000 mL
• Due to density, 1000 mL x 1.0 g/mL = 1000 g

This property is useful in many chemical calculations where masses are required instead of volumes.

Mastering Moles Calculation

Calculating moles is an essential part of chemistry. It allows us to quantify the number of particles in a given mass of substance. To calculate the number of moles, you use the formula:

• Number of moles = Mass of substance / Molar mass

For example, referring to 1 liter of water that weighs 1000 g:
Using water's molar mass (18.016 g/mol), the mole calculation is:

• Number of moles = 1000 g / 18.016 g/mol
• This results in approximately 55.5 moles of water.

This calculation helps one understand the amount of molecules involved in reactions and how they relate to the mass of substances.