How many moles of propane gas would be present in 11 grams
of the gas at standard conditions?

The molar mass is usually referred to with
M
, while the mass is referred to as
m
. The amount of substance is
n
. This gives you the following relationship:
=
M
=
m
n

Since you have given (C3H8)=11 g
m
(
C
3
H
8
)
=
11

g
and you already looked up (C3H8)=44.1 gmol−1
M
(
C
3
H
8
)
=
44.1

g
m
o
l
−
1
, you can use this formula to determine (C3H8)
n
(
C
3
H
8
)
.

In this question it is quite hard to explain the use of significant figures. Those are used to imply a certain inaccuracy. Not enough information is given by the question, as of how accurate the measurement is. It is a mere exercise of converting one property into another. Here you should not worry about it.

1.from liquid state to gaseous state is evaporation 3.solid to liquid is melting 5. solid to gaseous state is sublimation 6. gas to solid state is decomposition 7. a change of state is known as the states of matters

Mg-26 and mg-24 are pair of isotopes. isotopes are defined as atoms of the same element having same atomic number but different mass number. i hope that was .