YR 9 -Chemistry revision - Chemical formulae

YR 9 -Chemistry revision - Chemical formulae

Moles

• A mole is just a (very large) number of particles.

• Amount of substance is measured using a unit called the mole (mol for short) and given the symbol n.

• One mole is roughly 6×10^23 particles which is Avagadro's constant

Molar mass

• Molar mass is just the same as relative molecular mass (Mr)

• Molar Mass of CaCO3 is 40.1 + 12 + (3 x 16) = 100.1g/mol

• Moles= Mass/(Molar Mass (Mr))

Multiple Choice

How many moles are in 5.8g of CaCO₃?

• 0.58

• 0.058

• 5.8

• 0.0058

Multiple Choice

Calculate the mass of 0.36 moles of CaCO₃.

• 3.6

• 36

• 0.36

• 0.036

Multiple Choice

A molecule has a mass of 7g and its number of moles is 0.237. What is the molecular mass of this molecule?

• 30

• 1.7

• 0.03

• 0.30

Moles and volume

• Moles=Conc. ×Volume

Multiple Choice

What would the concentration be if 3 moles where dissolved in 3 dm³?

• 1

• 9

• 100

• 0.09

Multiple Choice

What mass of H2SO₄ is needed to produce 25cm³ of 25M solution

• 1

• 0.01

• 62.5

• 0.625

Multiple Choice

What mass of sodium hydroxide (NaOH) needs to be dissolved in 500cm³ of water to make a 2M solution

• 0.004

• 250

• 10

• 1000