Calculating Reacting Masses

Calculating Reacting Masses

Assessment

Assessment

Created by

Mr Boyle

Chemistry

5th Grade

21 plays

Hard

Student preview

quiz-placeholder

15 questions

Show answers

1.

Fill in the Blank

10 mins

15 pts

What mass of hydrogen is produced when 192 grams of magnesium reacts with excess hydrochloric acid?

Answer explanation

1) Write a balanced equation for the reaction:

Mg + 2HCl --> MgCl2 + H2

2) Calculate the number of moles of Mg:

n = m/M = 192/24 = 8 moles

3) Find molar ratio from equation:

1 (Mg) : 1 (H2), so 8:8

4) Calculate mass of hydrogen produced:

m = nM = 8 x 2 (H2 because hydrogen is diatomic) = 16 g

2.

Fill in the Blank

10 mins

15 pts

What mass of oxygen is needed to react with 8.5 grams of hydrogen sulfide? The products of this reaction are sulfur dioxide and water.

Answer explanation

1) Write a balanced chemical equation for the reaction:

2H2S + 3O2 --> 2SO2 + 2H2O

2) Calculate molar mass of hydrogen sulfide:

(1x32) + (2x1) = 34 g/mol

3) Calculate moles of hydrogen sulfide:

n=m/M = 8.5/34 = 0.25 moles

4) Work out molar ratio:

2:3 ratio, so 0.25 : 0.375 (divide 0.25 by 2 then multiply by 3). 0.375 moles of O2

5) Calculate the mass of oxygen:

m=nM = 0.375 x 32 = 12 g

3.

Fill in the Blank

10 mins

15 pts

What mass of potassium oxide is formed when 7.8 g of potassium is burned in oxygen?

Answer explanation

1) Write a balanced equation for the reaction:

4K + O2 --> 2K2O

2) Calculate moles of K:

n=m/M = 7.8/39 = 0.2 moles

3) Work out moles of potassium oxide from molar ratio:

4:2, so 2:1 ratio. 0.2 moles of K produces 0.1 moles of K2O

4) Calculate Mr of K2O:

(39x2) + (16x1) = 94 g/mol

5) Calculate mass of K2O:

m = nM = 0.1 x 94 = 9.4 g

4.

Fill in the Blank

10 mins

15 pts

Railway lines are welded together by the Thermite reaction, which produces molten iron.  What mass of iron is formed from 1 kg of iron oxide?

 

                                Fe2O3 + Al  --> Fe  +  Al2O3

Answer explanation

1) First step is to balance the equation given in the question:

Fe2O3 + 2Al  --> 2Fe  +  Al2O3

2) Calculate Mr of Fe2O3:

(56x2) + (16x3) = 160 g/mol

3) Calculate moles of iron oxide:

n = m/M = 1000/160 = 6.25 moles

4) Use molar ratio to determine moles of iron produce:

1:2 ratio, so 6.25 : 12.5 moles of Fe

5) Calculate mass of Fe:

m = nM = 12.5 x 56 = 700 g

5.

Fill in the Blank

10 mins

15 pts

What mass of oxygen is required to oxidise 10 grams of ammonia to NO?

Answer explanation

1) Write a balanced equation:

4NH3 + 5O2 --> 4NO + 6H2O

2) Calculate moles of ammonia:

n = m/M =10/17 = 0.588 moles

3) Work out moles of oxygen using molar ratio:

4:5 ratio, so 0.588 : 0.735 [Divide by 4 and multiply by 5]

4) Calculate mass of oxygen:

m = nM = 0.735 x 32 = 23.52 grams

Explore all questions with a free account

or continue with
Microsoft
Apple
Others
By signing up, you agree to our Terms of Service & Privacy Policy
Already have an account?

Find a similar activity

Create activity tailored to your needs using

Quizizz AI
Writing formula AS

20 questions

Writing formula AS

assessment

1st - 10th Grade

the reactivity series

15 questions

the reactivity series

assessment

5th Grade - Professio...

Salt

18 questions

Salt

assessment

5th - 8th Grade

Preparing soluble salt

20 questions

Preparing soluble salt

assessment

5th Grade

2E4 - Chemical Word Equation

10 questions

2E4 - Chemical Word Equation

assessment

5th Grade

The Chemistry Guru Final Quiz

20 questions

The Chemistry Guru Final Quiz

assessment

4th - 5th Grade

KS3 Making a salt

12 questions

KS3 Making a salt

assessment

2nd - 7th Grade

Effect of Heat on Salts

20 questions

Effect of Heat on Salts

assessment

1st - 12th Grade