4 Moles and Calculations Flashcards
Why is it important to mix reactants in the correct proportions?
This prevents contamination of the products by wasted (non reacted) reactants.
What is the definition of the relative atomic mass?
Relative atomic mass (RAM or Ar) is the weighted average mass of the isotopes of the element.
How is the relative atomic mass measured?
It is measured on a scale on which carbon-12 atom has a mass of exactly 12 units.
What is the definition of the relative formula mass?
Relative formula mass (RFM or Mr) is the sum of the relative atomic masses of all atoms present in the compound.
What is the definition of mole?
A number of atoms in 12 g carbon is defined as one mole.
What is the Avogadro’s number (Avogadro constant)?
Avogadro’s number is the exact number of atoms or particles in one mole substance = 6*10^23 atoms/particles.
What is Avogadro’s law?
Equal volumes of different gases at the same pressure and temperature will contain equal numbers of particles.
How many dm^3 and cm^3 are present in 1 liter of a gas?
1 liter = 1 dm^3 = 1000 cm^3
For what state of matter you can apply the Avogadro’s law?
Just for gases!
What is molar volume Vm?
Molar volume occupied by 1 mole gas at room temperature = 24 liters or 24000 cm^3.
2 moles of oxygen occupy 48 dm^3. What is the volume 2 moles of nitrogen would occupy at the same temperature and pressure?
48 dm^3
What is the empirical formula?
The simplest formula of a compound.
A compound contains 2,5 moles of nitrogen and 7,5 moles of hydrogen. What is the empirical formula of this compound?
NH3, it is ammonia.
What are the five steps during the calculation of a mass out from an equation?
- Write the balanced equation.
- Calculate the number of moles of given substance.
- Find out the ratio of needed substance to given substance.
- Find out the number of moles of needed substance.
- Calculate the needed mass.
