Chemistry stoichiometry problems

In summary, Graphite is a crystalline form of carbon used in lead pencils. The number of moles of carbon in a 315 mg piece of graphite is 0.315 g.
  • #1
triplepie
15
0
1. Graphite is a crystalline form of carbon used in "lead" pencils. How many moles of carbon are in 315mg of graphite?
2. 315mg = .315g

0.315 g C (1 mol C / !2 g C)
3. 0.026 mol C

2.1 Manganese is a transition element essential for the growth of bones. What is the mass in grams of 3.22 x 10^20 Mn atoms, the number found in 1 kg of bones?
2.2 3.22 x 10^20 Mn atom ( 1 mol Mn/ 6.022 x 10^23 atom Mn) = 5.35 x 10^-4 mol MN ( 54.94 g Mn/ 1 Mol Mn) = 293.77 x 10^-4 g Mn
2.3 293.77 x 10^-4 Mn

Im not sure how to find the number in 1 kg bone.
 
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  • #2
Your graphite result is wrong. The molecular weight of the Carbon element is 12.011. What did your "!2" value come from?
 
  • #3
I ignored the .011 because i was just practicing.
 
  • #4
but yeah, if i wanted it more accurate, I should have added .011
 
  • #5
Triplepie,
You are misusing your mathematical statements in the manganese solution but you seem to have the right idea about your choice and direction of the conversion ratios. Note that you reported too many significant figures.

Even if the calculation for manganese is correct (ignoring the quantity of significant figures), you should lose much credit for the way you expressed the steps. Make clear and unmistakable mathematical statements as steps; do not shove steps together and misuse the equality relation symbol.
 
  • #6
Ok, thanks, I'm not that good with sig figs and was going google on how to do it, can you tell me how to find 1kg in bone for the second problem, I don't know how to set it up.
 
  • #7
triplepie said:
Ok, thanks, I'm not that good with sig figs and was going google on how to do it, can you tell me how to find 1kg in bone for the second problem, I don't know how to set it up.

What? You just found the Mn in the 1 kg of bone. The only problem in your final result is the number of significant figures, as long as no other computational mistakes were made.
 
  • #8
Oh, so I just convert my answer from grams to kilogram?
 
  • #9
triplepie said:
Oh, so I just convert my answer from grams to kilogram?

Why? What was the actual question?
 

1. What is stoichiometry in chemistry?

Stoichiometry is a branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It involves using mathematical calculations to determine the amount of products that will be formed from a given amount of reactants.

2. How do you solve stoichiometry problems?

To solve stoichiometry problems, you need to follow a set of steps. First, write out the balanced chemical equation for the reaction. Then, determine the known and unknown quantities and convert them to moles. Use the mole ratio from the balanced equation to calculate the number of moles of the unknown substance. Finally, convert the moles of the unknown substance to the desired unit using the molar mass.

3. What is the purpose of using stoichiometry in chemistry?

The purpose of using stoichiometry in chemistry is to accurately predict the amount of products that will be formed in a chemical reaction, based on the amount of reactants used. It also helps in determining the limiting reactant and the excess reactant in a reaction, which is important for maximizing yield and minimizing waste.

4. What are some common units used in stoichiometry?

The most common units used in stoichiometry are moles (mol) for the amount of substance, grams (g) for mass, and liters (L) for volume. Other units may include molarity (M) for concentration and pressure (atm) for gases.

5. How is stoichiometry applied in real-life situations?

Stoichiometry is applied in various real-life situations, such as in the production of industrial chemicals, pharmaceuticals, and food products. It is also used in environmental sciences to determine the amount of pollutants produced in a reaction. In everyday life, stoichiometry is used in cooking and baking to ensure the correct ratio of ingredients for a recipe.

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