Answer:
Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. ... The spiral arms are sites of ongoing star formation and are brighter than the surrounding disc because of the young, hot OB stars that inhabit them.
Explanation:
Answer:
a. single replacement
Explanation:
Chemical equation:
Cd + H₂SO₄ → CdSO₄ + H₂
In given reaction Cd replace the hydrogen and form cadmium sulfate and hydrogen gas.
Single replacement:
It is the reaction in which one elements replace the other element in compound.
AB + C → AC + B
Other options are incorrect because,
Combustion:
In combustion reaction substances are burn in the presence of oxygen and form carbon dioxide and water.
Synthesis reaction:
It is the reaction in which two or more simple substance react to give one or more complex product.
A + B → AB
Double replacement:
It is the reaction in which two compound exchange their ions and form new compounds.
AB + CD → AC +BD
Answer: 1.67 kg
Explanation:
The quantity of heat required to raise the temperature of a substance by one degree Celsius is called the specific heat capacity.
Q = Heat absorbed=
= 
(1kJ=1000J)
m= mass of substance = ?
c = specific heat capacity = 
Change in temperature ,
Putting in the values, we get:
(1kg=1000g)
Thus the mass (in kg) of the copper sample is 1.67
Answer:
Single replacement reaction (aka single displacement reaction)
Explanation:
In a single replacement reaction, one element is substituted for another in a compound to create a new compound and a new element in the products. The general form is:
A + BC --> B + AC
In the case of this question, Cr and Fe "trade places."
Answer:
chemical change
Explanation:
chemical change requires energy in the form of heat or electricity.
