The lower the activation energy required for a chemical reaction
a) The reaction is exothermic since the overall enthalpy change is negative. this means that the system has lost energy to the environment, namely, the apparatus and due to drought.
b) We first calculate the number of moles in 3.55 grams of magnesium.
number of moles= mass/ atomic mass
=3.55/24
=0.1479 moles(to 4sf)
now, if 2 moles of magnesium give -1204kJ
How much energy is given by 0.1479 moles
= (0.1479×-1204kJ)
=-89.0358kJ (don't forget the negative sign)
c) two molesof MgO produces -1204kJ of energy
then -234kJ will be produced by
=(-234kJ×2moles)/1204kJ
=0.3887moles
one mole of MgO weighs 24+16=40
therefore the mass produced is 0.3887moles×40=15.548grams
(d) we first find the number of moles of MgO in 40.3 grams
number of moles=mass/RFM
=40.3g/40= 1.0075moles
if 2 moles of MgO give 1204 kJ then decomposing 1.0075 moles requires
(1.0075 moles×1204kJ)/2=606.515kJ
Answer:
2.94 x 
Explanation:
First we need to find out how many moles of ammonia there are, using the formula: Mass = mr x moles.
We know the mass is 83.1g, now we need to find the mR of ammonia - NH3.
N = 14, H = 1, so 14 + (3x1) = an mr of 17.
Moles = mass/ mr = 83.1/17 = 4.8882
Now we can multiply the moles by avogadro's constant to find the number of molecules:
4.8882 x (6.02 x 
) = 2.94 x molecules of ammonia
Answer: C
Explanation:
Indicators are organic weak acids or bases with complicated structures.
I check all of them. most of them correct but one
in question 6, the answer is the third choice. remember to find the neutrons, you take the atomic mass minus the atomic number. 38 - 18= 20
