Answer:
The ΔH of the reaction is + 12.45 KJ/mol
Explanation:
Mass of water= 100ml = 100g. (You should always assume 1cm3 of water as 1g)
heat capacity of water = 4.18 Jk-1 Mol-1
Change in temperature = (19.86 - 25.00) = -5.14 K (This is an endothermic reaction because of the fall in temperature)
Molar mass of NaHCO3 = 84 g/mol
Mole of NaHCO3 = 14.5 / 84 = 0.173 mol
Step 1 : Calculate the heat energy (Q) lost by the water.
Q = M x C x ΔT
Q = -100 x 4.18 x (-5.14)
Q = 2148.5 joules
Q = 2.1485 K J
Step 2: Calculating the ΔH of the reaction?
ΔH = Q / number of moles of NaHCO3
ΔH = 2.1485 / 0.173
ΔH = 12.42 KJ/mol
1 mole O2 -------------------- 6,02.10²³ molecules
0,25 mole O2 ---------------- x molecules
1 . x = 0,25 . 6,02.10²³
x = 1,50.10²³ molecules
Answer: the correct option is (C).
Explanation:
Covalent compounds have lower melting and boiling points due to presence of weak inter-molecular forces by which molecules are weakly associated to each other. Hence, melting and boiling of covalent compounds occurs at low temperatures.
Usually, Covalents compounds have following properties:
- They are brittle solids
- They do not conduct electricity
- They do not have rigid crystal structure.
- They exist in all states: solids, liquids and gases.
False because they can turn back to their original form a chemical change would be like burning paper it can’t be changed back to it’s original offer it’s burnt
Answer:
2.18x10^-9 M
Explanation:
From the question given,
Hydrogen ion concentration, [H+] = 4.59x10^-6 M
Hydroxide ion, [OH-] =?
The hydroxide ion concentration, [OH-] in the solution can be obtained as follow:
[H+] x [OH-] = 1x10^-14
4.59x10^-6 x [OH-] = 1x10^-14
Divide both side by 4.59x10^-6
[OH-] = 1x10^-14 / 4.59x10^-6
[OH-] = 2.18x10^-9 M
