The ideal gas equation and reacting masses

Question 1

What is the ideal gas equation?

Answer 1

pV=nRT

Question 2

What is the value of R in the ideal gas equation?

Answer 2

R is a constant and always has the value of 8.314mol^-1K^-1

Question 3

What are the units for temperature in the ideal gas equation?

Answer 3

K (kelvin)

Question 4

True or false? Each 1K rise in temperature is the same as a 1°C rise in temperature.

Answer 4

True

Question 5

What is the unit for volume in the ideal gas equation?

Answer 5

m³

Question 6

What is the unit for pressure in the ideal gas equation?

Answer 6

Pa (pascals)

Question 7

How do you convert cm³ in to m³?

Answer 7

Multiply by 10^-6

Question 8

How do you convert dm³ to m³?

Answer 8

You multiply by 10^-3

Question 9

How do you convert °C to K?

Answer 9

You add 273

Question 10

How do you covert KPa to Pa?

Answer 10

You multiply by 10³

Question 11

What are standard conditions?

Answer 11

273K and 1 atm

Question 12

If temperature is constant, what equation would you use?

Answer 12

P₁ V₁ = P₂ V₂

Question 13

If pressure is constant, what equation would you use?

Answer 13

T₁ / V₁ = T₂ / V₂

Question 14

If volume is constant, what equation would you use?

Answer 14

T₁ / P₁ = T₂ / P₂

Question 15

What is the meaning of the word, stoichiometry?

Answer 15

The ratio of the amount, in moles, of each substance

Question 16

What two things do chemists use balanced equations to find?

Answer 16

1. the quantities of reactants required to prepare a required quantity of a product
2. the quantites of products that should be formed from certain quantities of reactants

Question 17

What is the simple process to work out quanities from amounts and equations?

Answer 17

Step 1: Work out the amount in moles of whatever you can

Step 2: Use the equation given to work out the amount in moles of the unknown chemical

Step 3: Work out the unknown information required

Question 18

An experiment was conducted to try to fidentify an unknown group two metal. Explain how to work out the identity of the metal based on the results collected.

Results:

Mass of unknown metal = 0.14g

Volume of H₂ collected = 84 cm³

Answer 18

Step 1: Calculate the number of moles of H_2(g)

n= V/24000 n= 84/ 24000 = 0.00350 mol

Step 2: Calculate the amount of metal

It’s a 1:1 ratio so 0.00350 mol

Step 3: Work out the unknown information

n= m/M so M= m/n =0.14/0.00350

= 40g mol^-1

Ca has an atomic mass of 40.1 so the metal must be calcium

Question 19

What is a term to describe the maxiumum amount of product that can be formed from a reaction?

Answer 19

Theoretical yield

Question 20

Why is the theorectical yield often hard to achieve?

Answer 20

• The reaction may not have gone to completion
• Other reactions may have taken place alongside the main reaction
• purification of the product may have resulted in the loss of soe product

Question 21

True or false?

The actual yield obtained from a reaction is actually much higher than the theoretical yield

Answer 21

False

Question 22

What is the equation for calculating the percentage yield?

Answer 22

percentage yield = actual yield / theoretical yield x100

Question 23

In an equation, what is meant by a limiting reagent?

Answer 23

The reactant that is not in excess and that will be completely used up first and stop the reaction