Calculating Reacting Masses from Chemical Equations

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Questions and Answers

What is the mass of one mole of iron?

32g

28g

42g

56g (correct)

If the relative formula mass of nitrogen gas (N2) is 28, how many grams are in one mole of nitrogen gas?

28g (correct)

42g

56g

14g

Which equation can be used to convert between moles and mass?

moles = mass x relative atomic mass

mass = moles x relative atomic mass

moles = mass ÷ relative atomic mass (correct)

mass = moles ÷ relative atomic mass

If you have 42g of carbon, how many moles of carbon are present?

1 mole Signup and view all the answers

What does the mass of one mole of a substance represent?

The relative formula mass of the substance Signup and view all the answers

How many grams are in one mole of a substance if its relative formula mass is 16?

16g Signup and view all the answers

What does (aq) mean in a chemical equation?

Aqueous Signup and view all the answers

In a chemical equation, what does the relative formula mass (Mr) represent?

Sum of the relative atomic masses of the compound's atoms Signup and view all the answers

What is the unit used to measure chemical amounts?

Mole Signup and view all the answers

How do you balance a chemical equation if there are unequal numbers of elements on each side?

Use big numbers at the front of a compound Signup and view all the answers

What does a word equation represent in chemistry?

A chemical reaction using symbols Signup and view all the answers

What is the purpose of calculating relative formula masses in chemistry?

To quantify the mass of compounds Signup and view all the answers

What is the molar volume of any gas at room temperature and pressure?

24 dm3 Signup and view all the answers

If 6 moles of a gas occupy a volume of 144 dm3, what is the volume that 9 moles of the same gas would occupy at room temperature and pressure?

216 dm3 Signup and view all the answers

What is the formula to calculate the concentration of a solution in grams per decimeter cubed (g/dm3)?

Concentration (g/dm3) = Mass of solute / Volume Signup and view all the answers

If you have a common multiple formula of Fe2O4, what would be the empirical formula?

FeO2 Signup and view all the answers

What does the term 'empirical formula' represent?

The ratio of atoms in a compound in simplest whole numbers Signup and view all the answers

If you have the equation 2NaOH + Mg → Mg(OH)2 + 2Na, how many moles of Na would be formed if you had 2 moles of Mg?

4 moles Signup and view all the answers

What is the formula to calculate percentage yield?

(Amount of product produced / Maximum amount of product possible) x 100 Signup and view all the answers

In the equation Mg + 2HCl → MgCl2 + H2, how many moles of HCl are required to produce 1 mole of MgCl2?

2 moles Signup and view all the answers

If a solution has a concentration of 40 g/dm3 and a volume of 0.5 dm3, what is the mass of solute in the solution?

20 g Signup and view all the answers

Study Notes

Moles and Mass

One mole of iron has a mass of 55.85 grams.
Nitrogen gas (N₂) has a relative formula mass of 28, meaning one mole weighs 28 grams.
The equation to convert between moles and mass is Mass (g) = Moles × Relative Formula Mass (g/mol).
For 42g of carbon, use the relative atomic mass of carbon (12 g/mol), resulting in 3.5 moles of carbon present.
The mass of one mole of a substance represents its molecular or atomic weight in grams.

Relative Formula Mass

If a substance has a relative formula mass of 16, it contains 16 grams in one mole.
Relative formula mass (Mr) in a chemical equation represents the sum of the atomic masses of all atoms in a compound.

Chemical Equations and Balancing

The notation (aq) indicates an aqueous solution, meaning the substance is dissolved in water.
To balance a chemical equation, adjust the coefficients to ensure equal numbers of each type of atom on both sides of the equation.
A word equation represents the substances involved in a chemical reaction using their names instead of chemical formulas.

Calculating Concentration and Gas Volume

Calculating relative formula masses is essential for stoichiometry, determining quantities in reactions.
The molar volume of any gas at room temperature and pressure is 24 dm³.
If 6 moles of a gas occupy 144 dm³, the volume for 9 moles at the same conditions is 216 dm³.

Concentration and Empirical Formulas

The formula to calculate concentration in grams per decimeter cubed (g/dm³) is Concentration = Mass (g) / Volume (dm³).
For the formula Fe₂O₄, the empirical formula is FeO.
The term 'empirical formula' represents the simplest whole-number ratio of atoms in a compound.

Reaction Stoichiometry

In the equation 2NaOH + Mg → Mg(OH)₂ + 2Na, from 2 moles of Mg, 4 moles of Na would be formed.
The formula to calculate percentage yield is Percentage Yield = (Actual Yield / Theoretical Yield) × 100%.
In the reaction Mg + 2HCl → MgCl₂ + H₂, 2 moles of HCl are required to produce 1 mole of MgCl₂.
For a solution with a concentration of 40 g/dm³ and a volume of 0.5 dm³, the mass of solute is 20 grams.

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Description

Learn how to calculate reacting masses using experimental data and chemical equations. Understand how chemical equations can be interpreted in terms of moles. Practice calculating masses of reactants and products from balanced symbol equations.