Density = mass / volume
= 69g / 23 ml
= 3 g / ml.
Thus, the density of the sample is 3 grams per ml or 3g/ ml
Answer:
10. D
9. A
8. A or B
Explanation:
10. Calcium has 20 electrons, but the Calcium ion has 18 electrons.
9. The mass of electrons are negligible.
8. Electrons have a very small mass where some consider it to have no mass.
Answer:
The mass of the reactants compared with the mass of the products should be the same if the reactants are in stoichiometric amounts.
Explanation:
In this question, they ask about chemical reactions and the comparison of the mass of reactants and products. Firstly, it is necessary to introduce the mass conservation principle.
Mass conservation principle mentions that in a chemical reaction, the total mass of reactants is equal to the total mass of products (if the reaction is fully developed). It means mass is not created or destroyed, only transforms from reactants to products.
For example, the mass of sodium plus the mass of chlorine that reactswith the sodium equals the mass of the product sodium chloride.Because atoms are only rearranged in a chemical reaction, there mustbe the same number of sodium atoms and chlorine atoms in both thereactants and products.
Finally, we can conclude that The mass of the reactants compared with the mass of the products should be the same if the reactants are in stoichiometric amounts.
Answer:
2Al + 3ZnCl₂ → 3Zn + 2AlCl₃
Explanation:
Chemical equation:
Al + ZnCl₂ → Zn + AlCl₃
Balanced Chemical equation:
2Al + 3ZnCl₂ → 3Zn + 2AlCl₃
This is the example of single displacement reaction. Al displace the zinc and form aluminium chloride and zinc metal.
There are two Al three zinc and six chlorine atoms on both side of equation so it is correctly balanced.
Thus it completely follow the law of conservation of mass.
Law of conservation of mass:
According to the law of conservation mass, mass can neither be created nor destroyed in a chemical equation.
This law was given by french chemist Antoine Lavoisier in 1789. According to this law mass of reactant and mass of product must be equal, because masses are not created or destroyed in a chemical reaction.
Answer: Carbohydrates (carbo- = “carbon”; hydrate = “water”) contain the elements carbon, hydrogen, and oxygen, and only those elements with a few exceptions. The ratio of carbon to hydrogen to oxygen in carbohydrate molecules is 1:2:1.
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