Download presentation

Presentation is loading. Please wait.

Published byAbigail Lucy Price Modified over 2 years ago

1
MASS RELATIONSHIPS IN CHEMICAL EQUATIONS STOICHIOMETRY - the study of the mass and amount relationships between reactants and products in a chemical reaction.

2
EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 : CO 2(g) + LiOH (s) Li 2 CO 3(aq) + H 2 O (l) Step 1: Write a balanced chemical equation

3
EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 : Step 2: Write what has been given, write what is unknown/needed. EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 :

4
Step 3: Find the number of moles of each given/known compound. EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 :

5
Step 4: Set up a mole ratio in order to solve for the number of moles of unknown (LiOH) required. EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 :

6
Step 5: Find the mass of lithium hydroxide required by using the moles and molar mass. EXAMPLE 1: Determine the mass of lithium hydroxide required to react with 8.8 x 10 2 g of CO 2 :

7
EXAMPLE 2: An airbag is inflated with nitrogen produced from the decomposition of sodium azide, NaN 3. The mass of N 2 in a fully inflated airbag is 87.5g. What mass of NaN 3 is required to produce this mass of N 2 ? STEP 1: Write out the balanced chemical equation & state what is given/needed. EXAMPLE 2: An airbag is inflated with nitrogen produced from the decomposition of sodium azide, NaN 3. The mass of N 2 in a fully inflated airbag is 87.5g. What mass of NaN 3 is required to produce this mass of N 2 ?

8
STEP 2: Find the number of moles of the known (N 2 ). EXAMPLE 2: An airbag is inflated with nitrogen produced from the decomposition of sodium azide, NaN 3. The mass of N 2 in a fully inflated airbag is 87.5g. What mass of NaN 3 is required to produce this mass of N 2 ?

9
STEP 3: Use the balanced equation to find the mole ratio of the known/given substance to moles of unknown/needed substance (NaN 3 ).

10
EXAMPLE 2: An airbag is inflated with nitrogen produced from the decomposition of sodium azide, NaN 3. The mass of N 2 in a fully inflated airbag is 87.5g. What mass of NaN 3 is required to produce this mass of N 2 ? STEP 4: Find the mass of sodium azide required by using the moles and molar mass. EXAMPLE 2: An airbag is inflated with nitrogen produced from the decomposition of sodium azide, NaN 3. The mass of N 2 in a fully inflated airbag is 87.5g. What mass of NaN 3 is required to produce this mass of N 2 ?

11
No way!! Do you think that in the chemistry lab that we always get the amount of product that we calculate?

12
actual amount of a product expressed as a % of the theoretical amount of that substance % Yield

13
Terms: Theoretical yield: The amount of product predicted by stoichiometry. Actual yield: The amount of product produced through experimenting. Percentage yield:

14
Example # 1 HBrO 3 (aq) + 5HBr(aq) → 3H 2 O(l) + 3Br 2 (aq) 20.0g of HBrO 3 is reacted with excess HBr. a) What is the theoretical yield of Br 2 for this reaction? b) If 47.3g of Br 2 is produced, what is the percentage yield for Br 2 ? Answers: a) 74.4 g b) 63.6%

15
Example # 2 Using Hg(NO 3 ) 2 (aq) + Na 2 S(aq) → HgS(s) + 2NaNO 3 (aq), If 3.45x10 23 molecules of Hg(NO 3 ) 2 are reacted with excess Na 2 S, what mass of HgS can be expected if this process occurs with 97.0% yield? Answer: 129g

16
Application of Percentage Yield o Very important for chemical engineers who must produce large quantities of product. o An increase in percentage yield can result in increased profits. Percentage Purity o Typically applied to pharmaceuticals and the mining industry. Using Percent Yield

17
What do your numbers mean? A percentage yield less than 100% means o Other side reactions are happening at the same time that are not expected. o Decomposition of reactants or unreacted reactants = Realistic A percentage yield greater than 100%: o You have created matter (impossible) = Experimental error

18
HOMEWORK:

Similar presentations

Presentation is loading. Please wait....

OK

Chapter 12--Stoichiometry

Chapter 12--Stoichiometry

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on natural and manmade disaster Ppt on elections in india download film Ppt on online banking Ppt on marketing plan Ppt on speed control of 3 phase induction motor Ppt on quality education for all Ppt on aravind eye care system Keynote opening ppt on iphone Ppt on ram and rom hyper Ppt on environmental issues in chennai