I’m not sure if there was important information in the question before this one, but the answer based on the info I have is B.
The density of water is 1kg/L. Since the density of the block is less, it will float.
Answer:
7.5 g of hydrogen gas reacts with 50.0 g oxygen gas to form 57.5 g of water.
Explanation:
Here we have the check if the mass of the reactants is equal to the mass of the products.
Reactants

Products

The data is consistent with the law of conservation of matter.
Reactants

Products

The data is not consistent with the law of conservation of matter.
Reactant

Products

The data is not consistent with the law of conservation of matter.
Only the first data is consistent with the law of conservation of matter.
<h3>Further explanation</h3>
Basic oxides ⇒ metal(usually alkali/alkaline earth) +O₂
L + O₂ ⇒ L₂O
L + O₂ ⇒ LO
Dissolve in water becomes = basic solution
L₂O+H₂O⇒ 2LOH
LO + H₂O⇒ L(OH)₂
So the basic oxides : Na₂O and MgO
Na₂O + H₂O⇒NaOH
MgO +H₂O⇒Mg(OH)₂
The aqueous solution of CO₂(dissolve in water)
CO₂ + +H₂O⇒ H₂CO₃(carbonic acid)
Volume=Mass over density. V= 220/55. V=4cm^3
Nano particles are very small and can not be seen with eyes measuring between 1 to 100 n m. Because of their small size, they can't be made from macroscopic tools.
<h3>
What are particles? </h3>
These refers to those particles whose size lie between 1 to 100 n m. They are extremely small and often can not be seen with the eyes.
Owing to the fact that these particles are very small , they can not be created with very large substances.
Learn more about particles: brainly.com/question/9220200?