Answer: -
3.151 M
Explanation: -
Let the volume of the solution be 1000 mL.
At 25.0 °C, Density = 1.260 g/ mL
Mass of the solution = Density x volume
= 1.260 g / mL x 1000 mL
= 1260 g
At 25.0 °C, the molarity = 3.179 M
Number of moles present per 1000 mL = 3.179 mol
Strength of the solution in g / mol
= 1260 g / 3.179 mol = 396.35 g / mol (at 25.0 °C)
Now at 50.0 °C
The density is 1.249 g/ mL
Mass of the solution = density x volume = 1.249 g / mL x 1000 mL
= 1249 g.
Number of moles present in 1249 g = Mass of the solution / Strength in g /mol
= 
= 3.151 moles.
So 3.151 moles is present in 1000 mL at 50.0 °C
Molarity at 50.0 °C = 3.151 M
I think the answer is choice D
Experiments test the scientists' ideas.
Answer:
Final pressure in (atm) (P1) = 6.642 atm
Explanation:
Given:
Initial volume of gas (V) = 12.5 L
Pressure (P) = 784 torr
Temperature (T) = 295 K
Final volume (V1) = 2.04 L
Final temperature (T1) = 310 K
Find:
Final pressure in (atm) (P1) = ?
Computation:
According to combine gas law method:

⇒ Final pressure (P1) = 5,048.18877 torr
⇒ Final pressure in (atm) (P1) = 5,048.18877 torr / 760
⇒ Final pressure in (atm) (P1) = 6.642 atm