2 and a half
250 x 2 =500
250/2=125
and 125 is a half of 250
so your answer is
2 and a half
<u>Answer:</u> The
for the reaction is -1406.8 kJ.
<u>Explanation:</u>
Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.
According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.
The chemical reaction for the formation reaction of
is:

The intermediate balanced chemical reaction are:
(1)
( × 6)
(2)
( × 3)
(3)
( × 2)
(4)

The expression for enthalpy of formation of
is,
![\Delta H^o_{formation}=[6\times \Delta H_1]+[3\times \Delta H_2]+[2\times \Delta H_3]+[1\times \Delta H_4]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Bformation%7D%3D%5B6%5Ctimes%20%5CDelta%20H_1%5D%2B%5B3%5Ctimes%20%5CDelta%20H_2%5D%2B%5B2%5Ctimes%20%5CDelta%20H_3%5D%2B%5B1%5Ctimes%20%5CDelta%20H_4%5D)
Putting values in above equation, we get:
![\Delta H^o_{formation}=[(-74.8\times 6)+(-185\times 3)+(323\times 2)+(-1049\times 1)]=-1406.8kJ](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Bformation%7D%3D%5B%28-74.8%5Ctimes%206%29%2B%28-185%5Ctimes%203%29%2B%28323%5Ctimes%202%29%2B%28-1049%5Ctimes%201%29%5D%3D-1406.8kJ)
Hence, the
for the reaction is -1406.8 kJ.
Answer is: 2. dillute acids feel slipper.
1) Acids are corrosive is correct. For example hydrochloric acid (HCl) will react with most metals.
2) Dillute acids feel slippery is not correct. Bases, for example solution of sodium hydroxide feels slipery.
3) Acids have a distinctly sour taste is correct. For example, vinegar is mixture of acetic acid (CH₃COOH) and water (H₂O). Vinegar is colourless liquid with sour taste and pungent smell, freezing point of the vinegar is lower than glacial acetic acid.
4) Acids have more hydronium ions than hydroxide ions is correct. Because acid gives a lot of hydrogen cations (H⁺), pH (pH = -log[H⁺]) is lower than seven (acidic solution).