Stoiciometry. Finding mass and formula

[seru eman]

PROBLEM:
0.20 moles of C?H?N? + 60,7 g O2 --> 35,2 g CO2 + 25,2 g H2O + ? g NO2

how many grams of the molecule C?H?N? did we have before the reaction?

Find the forumla.

ANSWER:
18,1g, C4H14N2

BUT:
how do you solve it?

Thanks in advance!

 

[The Bob]

PROBLEM:
0.20 moles of C?H?N? + 60,7 g O2 --> 35,2 g CO2 + 25,2 g H2O + ? g NO2

how many grams of the molecule C?H?N? did we have before the reaction?

Find the forumla.

ANSWER:
18,1g, C4H14N2

BUT:
how do you solve it?

Thanks in advance!

Try it mathematically. Start by making everything in the same units, e.g. all in moles. Then compare the coefficents of each compound that contains the same element, e.g. Equate the carbons - 0.2 C_x = 0.8 C. Then think about elements and how they work, e.g. if you have 2CO₂ this is the same as saying there are 2 carbon atoms and 4 oxygen atoms or C₂O₄. Obvious the mole contains more than just one molecule of a substance, which is what I am implying, but it will allow you to make this relationship that will help you to solve the problem. If it really gets to you, say that 2 moles of CO₂ is the same as 1 mole of C₂O₄.

From the equation, I originally wrote, x = 4, which is the number of carbon atoms you need per mole (as per your solutions), as 0.8 C = 0.2 C_x = 0.2x C (if we use the logic from earlier).

Hope this helps with the solution, not necessarily the chemistry.

The Bob (2004 ©)

P.S. I reckon the mass of NO₂ is 18.3g not 18.1g

 

[Blueshift5]

To solve this problem, you will need to use stoichiometry, which is the quantitative relationship between reactants and products in a chemical reaction. First, you will need to balance the chemical equation by making sure that there are equal numbers of each element on both sides of the equation.

In this case, we have 1 mole of C?H?N? reacting with 60.7 g of O2 to produce 35.2 g of CO2, 25.2 g of H2O, and an unknown amount of NO2. Using the molar mass of each compound, we can convert moles to grams and determine the amount of C?H?N? present before the reaction.

To find the molar mass of C?H?N?, we need to add up the atomic masses of each element in the compound. The atomic mass of C is 12.01 g/mol, H is 1.01 g/mol, and N is 14.01 g/mol. Therefore, the molar mass of C?H?N? is 27.03 g/mol.

Next, we can use the given information of 0.20 moles of C?H?N? to calculate the mass present before the reaction:

0.20 moles x 27.03 g/mol = 5.41 g C?H?N?

So, we had 5.41 grams of C?H?N? before the reaction.

To determine the formula of the compound, we can use the molar ratios from the balanced equation. For every 1 mole of C?H?N? reacting, we produce 1 mole of CO2, 1 mole of H2O, and an unknown amount of NO2. This means that the ratio of C?H?N? to CO2 is 1:1, and the ratio of C?H?N? to H2O is also 1:1. Therefore, the formula of C?H?N? is C4H14N2, as we have 4 carbon atoms, 14 hydrogen atoms, and 2 nitrogen atoms.

In conclusion, using stoichiometry, we can determine that the amount of C?H?N? present before the reaction was 5.41 grams, and the formula of the compound is C4H14N2.