Stoichiometery+calculation+involvingMoles,+Mass,+Gas+volume+and+Molecules

= = Topic: Stoichiometery calculations involving Moles, Mass, Gas volume and Molecules.

REVIEW:

__Stoichiometry:__ the relatiobship between the amount of reactants used in a chemical reaction and the amounts of products product by the reaction.

__ Coefficients : __ coefficient can equal: - # molecules - # atoms -# moles __Example:__ 4NH 3(g) + 5O 2(g) 6H 2 O (g) + 4NO (g)
 * 4 molecules NH 3(g) + 5 molecules O 2(g) [[image:0370100202.jpg width="68" height="33"]]6 molecules H 2O (g) + 4 molecules NO(g)
 * 4 (6.022E23) NH 3(g) + 5 (6.022E23) O 2(g)[[image:0370100202.jpg width="80" height="27"]] 6 (6.022E23) H 2 O (g) + 4 (6.022E23) NO (g)
 * 4 mole NH 3(g) + 5 mol O 2(g) [[image:0370100202.jpg width="63" height="30"]]6 mole H 2 O (g) + 4 mole NO (g)

TEXT:

__Stoichiometery calculations__: to find how much of chemical #1 is involved in a chemical reaction based on the amount of chemical #2 involved

__Use diagram to explan the relationship between two chemicals:__
Mole of chemical #1 The bridge is: Moles  Mole of chemical #2

Explanation:

The relationship between the moles of chemical #1 and the moles of chemical #2 is centreal to each calculation. A good way to
to think about this kind of questions is: to visualize the connecation between to chemicals. If you want to slove problems, find out the moles is the most important part. Therefor, the bridge of two chemicals is "MOLES"

Examples: 1. Nitromethane, a fuel occasionally used in some drag racers, burns according to the reaction.

4CH 3 NO 2(g) + 3O 2(g) 4CO 2(g) + 6H 2 O + 2N 2(g) a) What mass of H 2 O is produced when 0.150g of 4CH 3 NO 2 is burned? b) What combined volume of gas at STP is produced if 0.316 g of CH 3 NO 2 is burned? What do you do? c) What volume of O 2(g) at STP is required to produce 0.250g of CO? What do you need to do? d) What mass of H 2 O (g) is produced when 0.410g of CO is produced? __ The step should following when we do this kind of questions: :__

a) What are you conversion steps (start with what is unknown)? g CH 3 NO 2 -- mol CH 3 NO 2  -- mol H 2 O -- g H 2 O

Therefor: 0.15g CH 3 NO 2 * 1mol CH 3 NO 2 /61.0 g CH 3 NO 2 * 6 mol H 2 O/4 mol CH 3 NO 2 * 18 g H 2 O/1 mol H 2 O g of H 2 O = 0.0664 g H 2 O

b) g CH 3 NO 2 --- mol CH 3 NO 2 --- (4 mol CO 2 / 4mol CH 3 NO 2 ) --- mol CO 2 ---L CO 2 0.136g CH 3 NO 2 * 1 mol CH 3 NO 2 / 61.0g CH 3 NO 2 * 4 mol CO 2 / 4 mol CH 3 NO 2 * 22.4L CO 2 / 1mol CO 2 = 0.1162 L CO 2

g CH 3 NO 2 --- mol CH 3 N0 2 --- (2 mol N 2 / 4 mol CH 3 NO 2 ) --- mol N 2 --- L N 2 0.31g CH 3 NO 2 * 1 mol NO 2 / 61.0 g CH 3 NO 2 * 2 mol N 2 /4 mol CH 3 NO 2 * 22.4L/ 1mol N 2 = 0.0528 L N 2 L CO 2 and N 2 = 0.1662 L CO 2 + 0.0582 L N 2 Total gas produced = 0.174L

c) What volume of O 2(g) at STP is required to produce 0.250g CO 2(g) ? What do you need to do? g CO 2(g) * mol CO 2(g) / g CO 2(g) * 3 mol O 2(g) / 4 mol CO 2(g) * 22.4L O 2(g) / 1 mol O 2(g) L O 2(g) = 0.250g CO 2(g ) * 1 mol CO 2(g) / 44.0g CO 2(g) * 3 mol O 2(g) / 4 mol CO 2(g) * 22.4L CO 2(g) / 1 mol O 2(g)  = 0.0955L CO 2(g)  d) What mass of H 2 O (g) is produced when 0.410g of CO 2(g) is produced? g H 2 O (g) = 0.410g CO 2(g) * 1mol CO 2(g) / 44.0g CO 2(g) * 6 mol H 2 O (l) / 4 mol CO 2(g) * 18.0g H 2 O (l) / 1mol H 2 O (l) = 0.252gL CO 2(g)

__The points we need care about during the calculation: __
 * CANCELATION
 * SIG FIG