Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: xstellarx on December 29, 2007, 02:23:53 PM

hi. i have a 25 item scavenger hunt for chemistry. i found most of the items accept a few. it would be great if you guys could help me out. thanks!!
3. the mass of sodium chloride that would be produced when 2.3 g of sodium reacts with .56 L of chlrine gas. Assume STP and 100% yield. Calculations and balanced equation required.
16. a hydrocarbon with molecular weight > 100. common name, chemical name, chemical formula.
18. an amount of water whose temperature would change 15 degrees C when it absorbed 630 calories of heat energy. calculations required (am i using a formula with vaporization? or something along those lines)

3. the mass of sodium chloride that would be produced when 2.3 g of sodium reacts with .56 L of chlrine gas. Assume STP and 100% yield.
Start with balanced eqn  then consider limiting reagents

Paper chromatography is an analytical technique (however, not used that often these days) for separating and identifying mixtures that are often coloured, especially pigments. The solvent front carries the solutes depending on their molecular weights. Thus, lighter material is carried further as opposed to heavier fractions
 heat required = mass x specific heat x temperature rise

3. the mass of sodium chloride that would be produced when 2.3 g of sodium reacts with .56 L of chlrine gas. Assume STP and 100% yield.
Start with balanced eqn  then consider limiting reagents
we havent learned how to balance equations yet.. ive looked it up in my textbook and review but its so confusing. i cant quite understand it

1. So called skeletal equation is: Na + Cl_{2} → NaCl. Note Cl is not balanced.
2Na + Cl_{2} → 2NaCl  Now it is balanced :)
You need to work out how many moles of Na and Cl_{2} you have (for Cl_{2} this will involve using gas law).

ok so to figure out a mole of something i would do a ratio right? i learned about moles in september so its kinda fuzzy lol. n then after i convert them what do i do next?

m_{Na} = 2.3g. M_{Na}(molar mass) = 22.99gmol^{1}  so you have 2.3/22.99 = 0.1mol
At STP 0.56L Cl_{2} is 0.0246mol.
2Na + Cl_{2} → 2NaCl
Cl_{2} is the limiting reagent...looking at numbers only ~half of Na will react. Now use ratios. If 1 mol Cl_{2} gives 2 mol NaCl (as shown in rxn eqn), how many will 0.0246 mol give?

HINT: The formula for you hydrocarbon = 100g is C7H16 from the CnH2n + 2 ruleor C(7) + H2(7) + 2 = C7H16
7(12) = 84
16(1) = 16
84 + 16 = 100
Now figure out the structure and the name

MY BAD...question states hydrocarbon greater than 100....tht is easier...
CnH2n+2 is even easier....just use C8H18...and that is an easy one let me knw what name and weight you get.
Think I need a break making mistakes now....LOL

For 18. just use the equation Q=MC(delta T)

Yes you sure are and you are solving for m. You can check your answer in this calculator: http://hyperphysics.phyastr.gsu.edu/hbase/thermo/spht.html