C5

Question 1

what is a mole?

Answer 1

the name given to a certain number

the unit for an amount of a substance

Question 2

what is one mole?

Answer 2

The unit for amount of substance is called the mole, shown as mol. One mole of atoms, ions or molecules is around 6 × 1023 (6 followed by 23 zeroes). This is the same number as the number of carbon atoms in 12 g of carbon.

Question 3

how can you calculate the number of moles?

Answer 3

relative formula mass of element or compound

Question 4

what the relative mass?

Answer 4

the relative atomic mass of an element is the avergae mass of an atom of the element compared to the mass of 1/12th of n atom of carbon12

Question 5

what is molar mass

Answer 5

The molar mass is the relative formula mass of a substance in grams (measured in g/mol)
The molar mass of a substance is its relative formula mass in grams. The unit for molar mass is g/mol.

Question 6

how can you find the relative formula mass?

Answer 6

To find the relative formula mass (or Mr) of a substance, you add together the relative atomic mass for all the atoms shown in its chemical formula.

Question 7

what does it meant to conserve mass?

Answer 7

Mass is never lost or gained in chemical reactions. We say that mass is always conserved. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.

Question 8

what are two common types of reaction that show conservation of mass

Answer 8

reactions where gas or water are lost during heating - such as the thermal decomposition of calcium carbonate to make calcium oxide and carbon dioxide

reactions where a gas is gained during the reaction - such as heating magnesium in air to make magnesium oxide

Question 9

how can you calculate the number of moles?

Answer 9

number of moles = mass ÷ molar mass