Answer: negative , from , to , exothermic
Explanation:
An endothermic reaction is a type of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.
An Exothermic reaction is a type of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.
Endothermic reactions are those in which heat is absorbed by the system from the surroundings and exothermic reactions are those in which heat is released by the system to the surroundings. 
for Endothermic reaction is positive and
As on dissolution of salt, the temperature of water increases, the heat has been released from system into surroundings and thus is negative.
Answer:
Molecular formula is C₂₆H₃₆O₄
Explanation:
The compound is 75.69 % C, 8.80 % H and 15.51 % O. This data means, that in 100 g of compound we have 75.69 g, 15.51 g and 8.80 g of, C, O and H, respectively. We know the molar mass of the compound, so we can work to solve the moles of each element.
In 100 g of compound we have 75.69 g C, 15.51 g O and 8.80 g H
In 412 g of compound we would have:
(412 . 75.69) / 100 = 311.8 of C
(412 . 15.51) / 100 = 63.9 g of O
(412 . 8.80) / 100 = 36.2 g of H
Now, we can determine the moles of each, that are contained in 1 mol of compound.
312 g / 12 g/mol 26 C
64 g / 16 g/mol = 4 O
36 g / 1 g/mol = 36 H
Molecular formula is C₂₆H₃₆O₄
Answer:
Mass percentage → 0.074 %
[F⁻] = 741 ppm
Explanation:
Aqueous solution of flouride → [F⁻] = 0.0390 M
It means that in 1L of solution, we have 0.0390 moles of F⁻
We need the mass of solution and the mass of 0.0390 moles of F⁻
Mass of solution can be determined by density:
1g/mL = Mass of solution / 1000 mL
Note: 1L = 1000mL
Mass of solution: 1000 g
Moles of F⁻ → 0.0390 moles . 19g /1 mol = 0.741 g
Mass percentage → (Mass of solute / Mass of solution) . 100
(0.741 g / 1000 g) . 100 = 0.074 %
Ppm = mass of solute . 10⁶ / mass of solution (mg/kg)
0.741 g . 1000 mg/1g = 741 mg
1000 g . 1 kg/1000 g = 1kg
741 mg/1kg = 741 ppm
The answer is B but iam not sure about the answer
