Answer:
10425 J are required
Explanation:
assuming that the water is entirely at liquid state at the beginning , the amount required is
Q= m*c*(T final - T initial)
where
m= mass of water = 25 g
T final = final temperature of water = 100°C
T initial= initial temperature of water = 0°C
c= specific heat capacities of water = 1 cal /g°C= 4.186 J/g°C ( we assume that is constant during the entire temperature range)
Q= heat required
therefore
Q= m*c*(T final - T initial)= 25 g * 4.186 J/g°C * (100°C- 0°C) = 10425 J
thus 10425 J are required
Answer:
58.44 g of NaCl are needed.
Explanation:
Given data:
Mass of NaCl needed = ?
Volume of solution = 200 mL (200/1000 =0.2 L)
Molarity of solution = 5 M
Solution:
We will solve this problem through molarity formula.
Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.
Formula:
Molarity = number of moles of solute / L of solution
Now we will put the values.
5 M = moles of solute / 0.2 L
Moles of solute = 5 mol/L × 0.2 L
Moles of solute = 1 mol
Mass of sodium chloride:
Mass = number of moles × molar mass
Mass = 1 mol × 58.44 g/mol
Mass = 58.44 g
Thus, 58.44 g of NaCl needed.
Answer:
20 atm / (R . 321 K . i) = M
Explanation:
Osmotic pressure is a colligative property which is determined by the solute.
Solutes over solutions, can increase the osmotic pressure which is calculated like this:
P = M . R . T
where P is pressure, M is molarity, R the Universal Constant Gases and T, the absolute Temperature. We also have to consider the Van't Hoff factor, i, numbers of ions dissolved. Ionic salts determine more osmotic pressure than organic compounds, where i = 1. Then, the complete formula is:
π = M . R . T . i
To determine molarity, osmotic pressure divide all the terms:
20 atm / (R . 321 K . i) = M
R = 0.082 L.atm/mol.K
If you see all the units in R, they will be cancelled, so finally the answer will be mol/L, which is molarity. The i term has no unit!.
The answer is 1,2,3 and 4 ok this answer is correct
