Calculating the Mass (GCSE Chemistry)
Calculating the Mass
Calculating the Mass of A Solute in a Given Solution
- We can measure concentration using mass. We’ve just seen that we can measure concentration by working out the mass of the solute that is dissolved in a certain amount of volume. This means that concentration is in g/dm3.
- Equations can be rearranged. You can rearrange this equation in order to find out the mass of the solute or to find the volume of the solution. For this, we can use the triangle and cover up the part of the equation we want to find. Then we simply divide or multiply the other two elements of the equation.
Practice Question: James makes up a solution of potassium bromide with 40g of potassium bromide dissolved in 0.4 dm3 of water. Calculate the concentration in g/dm3 of James’ solution.
1. Use the equation. We use the equation concentration = mass / volume in this case as we want the concentration in g/dm3.
Concentration (g/dm3) = mass of solute (g) / volume of solvent (dm3)
2. Substitute in the values. We can use the question to put in the values that we already know. Make sure to give units with your answer.
Concentration = 40 / 0.4
Concentration = 100g/dm3
Practice Question: Peter has a solution of magnesium chloride which has a concentration of 125 g/dm3. The solution has a volume of 0.4 dm3. What is the mass of magnesium chloride which was dissolved in the water solution?
1. Write out the equation.
Concentration (g/dm3) = mass of solute (g) / volume of solvent (dm3)
2. Rearrange the equation. We want to make mass the subject of the equation.
concentration = mass / volume
mass = concentration x volume
3. Substitute in the numbers. Now we can put in the numbers from the question.
Mass = 125 x 0.4 = 50g
Mass of magnesium chloride = 50g.
Mass in chemistry refers to the amount of matter in an object, typically measured in grams (g) or kilograms (kg).
The mass of an object can be calculated by using a scale. Simply place the object on the scale and read the measurement to determine its mass.
Some common units of mass include:
Grams (g)
Kilograms (kg)
Pounds (lb)
Ounces (oz)
Mass and weight are not the same thing, although they are often used interchangeably. Mass refers to the amount of matter in an object, while weight refers to the force exerted on an object due to gravity. The weight of an object is equal to its mass multiplied by the acceleration due to gravity.
The mass of an object does not change with temperature, as mass is a measure of the amount of matter in an object and is not affected by temperature.
No, the mass of an object cannot be negative. Mass is a scalar quantity, meaning it has only magnitude and no direction.
The mass of a substance in a chemical reaction can be calculated by determining the mass of the reactants and the mass of the products and comparing the two. If the mass of the reactants is equal to the mass of the products, the reaction is said to be mass conserving.
The law of conservation of mass states that the total mass of the reactants in a chemical reaction must be equal to the total mass of the products. This means that the mass of a substance in a chemical reaction cannot be created or destroyed, only transformed from one form to another. When calculating the mass of a substance in a chemical reaction, it is important to consider the law of conservation of mass to ensure that the masses of the reactants and products are balanced.
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