20 g O2 x 1 mol O2/32 g O = 0.625 mol O2
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
1- Molar solutions: based on number of moles of chemical in 1 litre of solution
2- Weight % solution: the weight of chemical divided by the total weight of the solution (chemical + water) and multiplied by 100.
If the difference in electronegativtiy for the atoms in a bond are greater than 0.4,we consider the bond polar, if the electronegativity is less than 0.4, we consider it non polar. if there are no polar bonds, the molecule is non polar.
Answer:
2
Explanation:
Cells divide and reproduce in two ways, mitosis and meiosis. Mitosis results in two identical daughter cells, whereas meiosis results in four sex cells.
