Answer:
Oxygen in hydrogen peroxide oxidizes from -1 to 0.
Explanation:
Oxidation is the loss of electrons. The specie which is oxidized has has elevation in its oxidation state as compared in the reactant and the products.
The given reaction is shown below as:
Manganese in 
has oxidation state of +7
Manganese in 
has an oxidation state of +2
It reduces from +7 to +2
Oxygen in hydrogen peroxide has an oxidation state of -1.
Oxygen in molecular oxygen has an oxidation of 0.
Thus, oxygen in hydrogen peroxide oxidizes from -1 to 0.
Magnesium combined with chlorine.
How?
- Look at the question .Compound has -1 charge in it .Hence it contains Halogen.
- Looking at the options Option B and C contain Iodine and chlorine i.e halogens .
Now come to metals side.
- Potassium has valency 1(Look the Electronic configuration below)
Hence it will contain +1 charge which is omitted directly .
Now come to option C.
- Magnesium has charge +2(Look at EC below
Hence the compound formed is given by
Hence option C is correct.
Answer: C) Elements and pure compounds are homogeneous materials because they have a uniform composition throughout.
Explanation: Element is a pure substance which is composed of atoms of similar elements. Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.
Elements are compounds form homogeneous materials as they have uniform composition throughout and the components are evenly distributed throughout the material.
Mixtures are heterogeneous materials as they do not have uniform composition and the components are not evenly distributed throughout the material.
70.0 g. The decomposition of 125 g CaCO3 produces 700 g CaO.
MM = 100.09 56.08
CaCO3 → CaO + CO2
Mass 125 g
a) Moles of CaCO3 = 125 g CaCO3 x (1 mol CaCO3/100.09 g CaCO3)
= 1.249 mol CaCO3
b) Moles of CaO = 1.249 mol CaCO3 x (1 mol CaO/1 mol CaCO3)
= 1.249 mol CaO
c) Mass of CaO = 1.249 mol CaO x (56.08 g CaO/1 mol CaO) = 70.0 g
