Answer:
Explanation:
We are asked to convert an amount in grams to moles. To do this, we use the molar mass. This is the number of grams in one mole of a substance. It is the same value numerically as the atomic mass on the Periodic Table, however the units are grams per mole, not atomic mass units.
Look up the molar masses for the individual elements.
- Sodium (Na): 22.9897693 g/mol
- Oxygen (O): 15.999 g/mol
Look back at the formula: Na₂O. Notice there is a subscript of 2 after sodium. This means there are 2 atoms of sodium in every molecule, so we have to multiply sodium's molar mass by 2 before adding oxygen's.
- Na₂O: 2(22.9897693 g/mol)+ 15.999 g/mol = 61.9785386 g/mol
Set up a ratio using the molar mass.
Multiply by the given number of grams.
Flip the ratio so the grams of sodium oxide can cancel each other out.
The original measurement of grams given has 3 significant figures, so our answer must have the same. For the number we calculated, that is the hundredth place.
The 4 in the thousandth place tells us to leave the 8.
There are <u>2.48 moles of sodium oxide</u> in 154 grams, so choice A is correct.
Wax is susceptible to heat. Wax is responds to heat addition. The forces in the wax when heat is added are being broken off and are much lesser as its original state. Hope this answers the question. Have a nice day.<span />
It will react by being a chemical change because something new is formed
The half life of 131 i is 8.06 days
calculation
by use of concentration time equation for radioactive decay
In Nt/No = -Kt
where Nt/No is the fraction of the sample remaining at time T
convert 50.2% in decimal = 50.2/100 = 0.502
therefore = In 0.502 = - K 8.0 t
- 0.689 =-8.0 k
divide both side by 8.0
K = 0.860
t1/2 = 0.693/K
t1/2 = 0.693/0.860 = 8.06 days