ElectricPavlov

Oops....never mind.   I see you answered your posted question in the body of your submission......

You're welcome !   Hope you can figure them out now.....

Third one:

(realize that oxygen gas is O2   not elemental oxygen O )

Propane gas

C3 H8  has a mole weight of     C x 3 + H x 8  =   12.011 x 3 + 1.008  x 8 = 44.097 gm/mole

   155 gm / 44.097 gm/mole =3.515 moles

  From the equation EACH mole of C3H8 requires FIVE moles of oygen gas

      3.515 x 5 = 17.575 moles of O2 required

Second one:

Oxygen mole weight 15.999 gm/mole           96 gm / 15.999 gm/mole = 6 moles of O

    from the equation you are using O2 so there is only THREE moles of O2

        each mole of O2 produces TWO moles of MgO from the equation

                          so you will get SIX moles of MgO

First one:

ONE mole of Cu is required for TWO moles of HNO3

You have  .150 mole of HNO3     so you need  .075 mole of Cu (copper) (half as much)

   Copper mole weight 63.546 gm/mole

63.546 gm/mole x .075 mole = 4.766 gm of Cu required

Chris has given you GA       G'A'  will be of proportionate length

14/35  = G'A' / 30

G'A' = 30  14/35 = 12 inches

SO it is like you have 6 cards      One black and 5 red

you draw a red, then what is the chance of the next draw is red.....?

   there are 5 cards left    4 are red and one is black

       4/5           is that how to view this ?

Not gonna tell how I did this.....

correct ...I am incorrect

For the SMALL boxes    3L = 4W      (3/2 L = 2W )

The LARGE CRATE   is     3L /  (2W + L)   = 3L/(3/2L+L) = 3L /( 5/2*L) =  6/5   (as Chris found)