Answer : Option D) the electrons in some metals pair up to create a magnetic field.
Explanation : Most of the metals are magnetic in nature including some exceptions. When the unpaired electrons get aligned with the magnetic field they posses magnetism. Also there are some paired electrons in metals which align themselves according to the magnetic field and create magnetism in them.
Answer:
The new volume of the gas is 21 L.
Explanation:
Volume of a gas is inversely proportional to its pressure at constant temperature such that,

or

We have,

It is required to find V₂. Using above law or Boyle's law such that :

So, the new volume of the gas is 21 L.
Answer:
2HNO3 +Na2CO3 → CO2 + H2O + 2NaNO3
Explanation:
Start with a balanced equation.
2H2 + O2 → 2H2O
Assuming that H2 is in excess, multiply the given moles H2O by the mole ratio between O2 and H2O in the balanced equation so that moles H2O cancel.
5 mol H2O × (1 mol O2/2 mol H2O) = 2.5 mol O2
Answer: 2.5 mol O2 are needed to make 5 mol H2O, assuming H2 is in excess.
Would it be lack of water and food?