Chemistry By Jocelyn Ventura

When salt is added to water, the property that is not expected to change is its non flammability. Adding salt to water does not affect its ability to extinguish fires or its resistance to burning.

According to the law of conservation of mass, the total mass of the reactants must be equal to the total mass of the products. In this reaction, 10g of A reacted with B to produce 25g of C. Therefore, the mass of B that reacted can be calculated by subtracting the mass of A from the total mass of the products: 25g - 10g = 15g. So, the correct answer is B. 15g.

The correct answer is A because compounds have a fixed ratio of elements by mass. Changing the formula of a compound would change the ratio of elements, which would result in a different compound and therefore a different reaction.

Dalton's Atomic Theory states that in an ordinary chemical reaction, no new atoms are created and no old ones are destroyed. This assumption explains the Law of Conservation of Mass, which states that the total mass of the reactants in a chemical reaction is equal to the total mass of the products. This means that the mass of the substances involved in a chemical reaction remains constant, supporting the idea that atoms are not created or destroyed during the reaction.

The formation of ash after burning indicates that the substance combined with another element to form a compound.

In a chemical reaction, the total mass of the reactants is equal to the total mass of the products. This is known as the law of conservation of mass. This means that even though the reactants may undergo a chemical change and rearrange their atoms to form new products, the total mass of the system remains constant. Therefore, the correct answer is D. mass.

When calcium and sulfur react, they combine in a mass ratio of 5:4. This means that for every 5 grams of calcium, 4 grams of sulfur are needed for a complete reaction. In this scenario, 10 grams each of calcium and sulfur are mixed. Since the ratio of calcium to sulfur is 5:4, it means that 8 grams of sulfur will react with all 10 grams of calcium. Therefore, 2 grams of sulfur will remain unreacted after the reaction.

The properties of the liquid that show it is a compound, not a mixture, are that it boils sharply and has a definite composition. Boiling sharply indicates that the liquid has a specific boiling point, which is characteristic of compounds rather than mixtures. Additionally, the fact that the liquid has a definite composition of 92% carbon and 8% hydrogen by mass further suggests that it is a compound with a fixed ratio of elements.

Based on the given information, we know that for every 3.0 g of hydrogen, there are 14 g of nitrogen in ammonia. Therefore, we can set up a proportion to find the amount of nitrogen needed to react with 0.15 g of hydrogen.

(14 g of nitrogen / 3.0 g of hydrogen) = (x g of nitrogen / 0.15 g of hydrogen)

Cross-multiplying and solving for x, we get:

x = (14 g of nitrogen / 3.0 g of hydrogen) * 0.15 g of hydrogen
x = 0.7 g of nitrogen

Therefore, the correct answer is C. 0.70 g.

Aluminium pots should not be used when preparing herbal medicines from plant leaves because aluminium can react with the compounds in the leaves and contaminate the medicine. It is recommended to use stainless steel or glass pots instead.

To determine the mass of D in the chemical equation, you need to add the masses of A and B, and then subtract the mass of C. This is because in a chemical reaction, mass is conserved. The total mass of the reactants (A and B) should be equal to the total mass of the products (C and D). Therefore, by subtracting the mass of C from the total mass of A and B, you can find the mass of D.

Salt is a compound that is formed when a metal and a non-metal combine chemically. It is a pure substance because it is made up of only one type of molecule. However, not all salts contain oxygen. Some salts, such as sodium chloride (table salt), do not contain oxygen. Therefore, statement C is incorrect.

The total mass of reactants and products will remain the same before and after the reaction because of the law of conservation of mass. According to this law, matter cannot be created or destroyed in a chemical reaction, only rearranged. Therefore, the total mass of the substances involved in the reaction will always remain constant.

In an electrolytic conductor, the current is carried by ions. In an electrolyte solution, the molecules of the solute dissociate into ions, which are then able to move and carry electric charge. These ions can be positively charged (cations) or negatively charged (anions), and they are responsible for conducting the current in the electrolyte. Therefore, the correct answer is D. ions.

Oxygen is most likely present in the jar because it supports combustion and allows the match to catch fire. Hydrogen, carbon dioxide, and carbon monoxide do not support combustion, so they would not cause the match to catch fire.

When copper is heated in the presence of air, it undergoes oxidation and forms copper oxide, which has a reddish black color. The increase in mass after heating is due to the addition of oxygen from the air to the copper. Therefore, the mass after heating is greater than the mass before heating.

When calcium and sulfur react in a mass ratio of 5:4, it means that for every 5 grams of calcium, 4 grams of sulfur will react. In this case, since we have 10 grams of both calcium and sulfur, there will be an excess of sulfur.

To find out how much sulfur will remain unreacted, we can set up a proportion:

5 grams of calcium reacts with 4 grams of sulfur

10 grams of calcium reacts with x grams of sulfur (x represents the amount of sulfur that will react)

By cross multiplying, we get:

5 * x = 10 * 4

x = 20 grams of sulfur will react

Since we initially had 10 grams of sulfur, and 20 grams will react, 10 - 20 = -10 grams of sulfur will remain unreacted. However, it is not possible to have a negative mass, so the correct answer is that no sulfur will remain unreacted.

The correct answer is B. kind and amount of element present. This is because the composition of a compound refers to the types of elements present in the compound and the ratio of these elements. The amount of each element present in the compound is also important in determining its composition. Therefore, both the kind and amount of elements present are necessary to fully describe the composition of a compound.

In the given question, it is stated that calcium combines with sulfur in a mass ratio of 5:4. This means that for every 5 grams of calcium, there will be 4 grams of sulfur. If 10 grams each of calcium and sulfur are mixed and heated in a closed vessel, the calcium will completely react with the sulfur according to the given ratio. Therefore, all of the calcium will be consumed during the chemical reaction, making option B, Calcium, the correct answer.

The dark violet crystal is an element because it undergoes a reaction where it transforms into a violet gas and then forms fine violet crystals. This indicates that the dark violet crystal is a pure substance that cannot be further broken down into simpler substances, which is a characteristic of an element.

An element is a pure substance that cannot be broken down into simpler substances by chemical means. When heated in the presence of air, some elements can react with oxygen and gain mass, such as iron rusting. On the other hand, a compound is a substance composed of two or more elements chemically combined. When heated in the presence of air, some compounds can decompose and lose mass, such as water evaporating into steam. Therefore, the statement that an element gains mass when heated in the presence of air while a compound loses mass when heated in the presence of air correctly distinguishes between an element and a compound.

The law of definite composition applies to a sample of ice. This law states that a compound is always composed of the same elements in the same proportions by mass. Ice is a compound made up of water molecules, which always have the same ratio of hydrogen to oxygen atoms. Therefore, the composition of ice is definite and follows the law of definite composition.

The correct answer is the law of mass conservation because this law states that in a chemical reaction, matter cannot be created or destroyed, it can only be rearranged. This means that the total mass of the reactants must be equal to the total mass of the products.

When copper reacts with oxygen to form copper (II) oxide, the mass of copper and the mass of oxygen combine to form the mass of copper (II) oxide. This is because mass is conserved in a chemical reaction, meaning that the total mass of the reactants is equal to the total mass of the products. Therefore, the mass of copper (II) oxide that forms is equal to the sum of the masses of copper and oxygen that combined.

The data in the table shows that the mass of compound AB varies depending on the masses of elements A and B. This indicates that the composition of AB is not constant and can vary. Therefore, option A, which states that AB has no definite composition, is the correct answer.