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Stoichiometric calculations

Stoichiometry is the calculation of the quantities of reactants and products in chemical reactions. It is also the numerical relationship between reactants and products. In representing chemical change showed how to write balanced chemical equations. By knowing the ratios of substances in a reaction, it is possible to use stoichiometry to calculate the amount of either reactants or products that are involved in the reaction. The examples shown below will make this concept clearer.

What volume of oxygen at S.T.P. is needed for the complete combustion of 2 dm 3 of propane ( C 3 H 8 )? (Hint: CO 2 and H 2 O are the products in this reaction (and in all combustion reactions))

  1. C 3 H 8 ( g ) + 5 O 2 ( g ) 3 C O 2 ( g ) + 4 H 2 O ( g )

  2. From the balanced equation, the ratio of oxygen to propane in the reactants is 5:1.

  3. 1 volume of propane needs 5 volumes of oxygen, therefore 2 dm 3 of propane will need 10 dm 3 of oxygen for the reaction to proceed to completion.

What mass of iron (II) sulphide is formed when 5,6 g of iron is completely reacted with sulphur?

  1. Fe ( s ) + S ( s ) FeS ( s )

  2. n = m M = 5 , 6 55 , 85 = 0 , 1 mol
  3. From the equation 1 mole of Fe gives 1 mole of FeS . Therefore, 0,1 moles of iron in the reactants will give 0,1 moles of iron sulphide in the product.

  4. m = n × M = 0 , 1 × 87 , 911 = 8 , 79 g

    The mass of iron (II) sulphide that is produced during this reaction is 8,79 g .

When we are given a known mass of a reactant and are asked to work out how much product is formed, we are working out the theoretical yield of the reaction. In the laboratory chemists never get this amount of product. In each step of a reaction a small amount of product and reactants is 'lost' either because a reactant did not completely react or some of the product was left behind in the original container. Think about this. When you make your lunch or supper, you might be a bit hungry, so you eat some of the food that you are preparing. So instead of getting the full amount of food out (theoretical yield) that you started preparing, you lose some along the way.

Sulphuric acid ( H 2 SO 4 ) reacts with ammonia ( NH 3 ) to produce the fertiliser ammonium sulphate (( NH 4 ) 2 SO 4 ) according to the following equation:

H 2 SO 4 ( aq ) + 2 NH 3 ( g ) ( NH 4 ) 2 SO 4 ( aq )

What is the maximum mass of ammonium sulphate that can be obtained from 2,0 kg of sulphuric acid?

  1. n ( H 2 SO 4 ) = m M = 2 000 g 98 , 078 g · mols - 1 = 20 , 39 mols
  2. From the balanced equation, the mole ratio of H 2 SO 4 in the reactants to ( NH 4 ) 2 SO 4 in the product is 1:1. Therefore, 20,39 mols of H 2 SO 4 of ( NH 4 ) 2 SO 4 .

    The maximum mass of ammonium sulphate that can be produced is calculated as follows:

    m = n × M = 20 , 41 mol × 132 g · mol - 1 = 2694 g

    The maximum amount of ammonium sulphate that can be produced is 2,694 kg .

Questions & Answers

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In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
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AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
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Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
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Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
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Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
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In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
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Answer
Feyisa
c
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Source:  OpenStax, Chemistry grade 10 [caps]. OpenStax CNX. Jun 13, 2011 Download for free at http://cnx.org/content/col11303/1.4
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