Answer:
A is the correct answer.
Explanation:
An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.
For example in case of Helium:
The 1st one diagram shows that arrow is pointing with in nucleus. The helium nucleus contain two protons and two neutrons. Thus maximum mass is present with in nucleus. while two electrons are revolve around the nucleus and mass of electron is negligible.
Molality can be expressed by moles of solute over
kilograms of solvent. The question asks the molality of 0.25m NaCl. 0.25m NaCl
is equal to 0.25 moles of NaCl over 1 kg of water.
Answer : The value of rate of reaction is 
Explanation :
Rate law : It is defined as the expression which expresses the rate of the reaction in terms of molar concentration of the reactants with each term raised to the power their stoichiometric coefficient of that reactant in the balanced chemical equation.
The given chemical equation is:

Rate law expression for the reaction is:
![\text{Rate}=k[NO]^a[O_2]^b](https://tex.z-dn.net/?f=%5Ctext%7BRate%7D%3Dk%5BNO%5D%5Ea%5BO_2%5D%5Eb)
As per question,
a = order with respect to
= 2
b = order with respect to
= 1
Thus, the rate law becomes:
![\text{Rate}=k[NO]^2[O_2]^1](https://tex.z-dn.net/?f=%5Ctext%7BRate%7D%3Dk%5BNO%5D%5E2%5BO_2%5D%5E1)
Now, calculating the value of rate of reaction by using the rate law expression.
Given :
k = rate constant = 
[NO] = concentration of NO = 
= concentration of
= 
Now put all the given values in the above expression, we get:


Hence, the value of rate of reaction is 
Answer:
MgF2 + Li2CO3 ---> MgCO3 + 2LiF
Explanation:
Answer:
The seven crystal systems are a method of classifying crystals according to their atomic lattice or structure. The atomic lattice is a three dimensional network of atoms that are arranged in a symmetrical pattern. The shape of the lattice determines not only which crystal system the stone belongs to, but all of its physical properties and appearance. In some crystal healing practices the axial symmetry of a crystal is believed to directly influence its metaphysical properties. For example crystals in the Cubic System are believed to be grounding, because the cube is a symbol of the element Earth.
Explanation:
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