plzz i really need help with these chemistry questions ..plzz help me thanks?

Question

6. Duralin is an alloy of aluminium containing
4:5% manganese, 3:5% copper, and 0:45%
magnesium. How much magnesium is present
in a 46 g sample of this alloy? Answer in units
of mol.



10. What is the molecular weight of 429 g of
lead(II) nitrite? Answer in units of g=mol.


13. Magnesium hydroxide is 54.87% oxygen by
mass. How much oxygen is in 180 g of the
compound? Answer in units of g.



14. How many moles of oxygen is this? Answer in
units of mol.


plzz give answers and if so work. thank you..

Answer 1

do you happen to go to Santiago High School and are you in either Dr. Lachman's or Mr. White's class? Because I am doing the online homework and you are asking the same questions.

Answer 2

OK - some of this is really simple if you remember the word "of" in math means to multiply.

So, in q. 6, if 0.45% OF the alloy is magnesium, then 0.45% OF 46g is magnesium so multiply. (Don't forget to change the % to a decimal before you multiply).

q.10 doesn't make sense. The molecular weight of lead(II) nitrate is not 429 g. I think the question should be "how many moles of lead(II)nitrate are contained in 429g. That would make this a gram to mole conversion problem. These are done by finding the molecular mass of the compound (Just add up the individual atomic masses). If you divide your grams by the molar mass you will have moles.

Lead (II) nitrate is Pb(NO3)2 so you need to use a periodic chart to look up the masses of of each element and multiply by the number of atoms of each element in the compound.

(1 x Pb plus 2 x N plus 6 x O to get the molar mass.)

q. 13 uses "of" again. If 54.87% OF the compound is oxygen, then 54.87% OF 180g is the mass of the oxygen so just multiply. Again, don't forget to change the % to a decimal before you multiply.

q. 14 is another gram to mole conversion. Once you have your answer in q. 13, divide by the atomic mass of oxygen (its and element so you just look it up on the periodic chart).

Answer 3

6. .45% of 46 g is 0.207 g of Mg. Since Mg's mol. wt. is 24.31 g/gmol, you get the no. of moles as 0.00852 by dividing wt. by mol. wt. => 46 g of your alloy has 0.00852 moles of Mg.

10.you first need to be clear that mol. wt. is the wt. of one molecule of a compound. So, it does not depend on the amount of the compound you have. the molecular wt. of any amount of lead nitrite is 253.2 g/gmol (207.2 for lead, 14 for niitrogen and 32 for oxygen.)

13. 98.766 g of oxygen.

14.O's atomic wt. is 16 g/gmol. So 98.766 g is 6.173 gmol od oxygen.

P.S: I hope i haven't just completed your chemistry homework... If I have, I hope you have understood the principles now.

Answer 4

6.
0.45%*46=0.207g of Mg
Mg molar mass 24.3050 g/mol
0.207/24.305=8.52*10^-3 mol of Mg

10.
Answer in units of g=mol ?

13.
54.87% of the mass is oxygen
so 54.87%*180=98.77g of oxygen

14.
molar mass of oxygen 16g/mol
98.77/16=6.16 moles of oxygen

Answer 5

a million. The Ar must be 192 if both isotopes were recent in suited 50 /50 mix. Hmm... you artwork it out. 2) The isotopes in elementary words variety interior the style of neutrons of their nucleus, and the chemical houses are determined with techniques from the electrons = style of protons.