Unit' is the word used to describe how something is measured. When researching a question in science, we collect data, interpret it, and share the results with other scientists. A common measurement system allows us to make direct comparisons instead of having to know things like how much a certain animal weighs.
Answer:
The time decreases steadily
Explanation:
We know that the rate of chemical reaction is defined as how fast or slow a chemical reaction proceeds. Hence a chemical reaction is said to proceed at a faster rate if it takes a lesser time for the reaction to get to completion.
There are certain factors that affects the rate of reaction, prominent among them is the concentration of reactants. Concentration simply means the amount of substance in a system.
Taking a look at the table given in the question, we will realize that the volume of HCl remained constant, the volume of thiosulphate increased steadily while the volume of water decreased steadily. Remember that concentration increases when less water is added to the system. This implies that the reactant concentration increases steadily. Hence, according to the collision theory, particles collide more frequently and the rate of reaction increases.
As the rate of reaction increases, it now takes a lesser time for the reaction to get to completion (indicated by the disappearance of the cross). Hence as we move down the table, it takes lesser and lesser time for the cross to disappear. This means that the column for time will decrease steadily.
Answer:
Co (assuming there's a typo in not capitalizing the first letter)
Explanation:
The elements are depicted in the periodic table. Those are fundamental atoms that are not bonded to anything else but exist in their natural states without forming a bond with anything. That said, we're interested in a monoatomic species listed (the species which consist from only one single atom).
Out of all the choices, we have Co, cobalt, which is a single atom and can be found as an element with the atomic number 27.
Carbonic acid, 
, consists of 3 different elements: hydrogen (atomic number of 1), carbon (atomic number of 6) and oxygen (atomic number of 8). It's a compound rather than an element, as it consists of several atoms bonded together.
Oxygen, 
, is also a molecule. It consists of more than a single atom, even though the two atoms are identical. We have a compound, oxygen gas, which consists of two same oxygen (O) atoms (or elements).
Hydroxide anion, 
, also consists of two elements: oxygen and hydrogen. It also contains a charge on it, so rather than being a molecule, this is now an ion. Since it consists of more than a single atom, this is not an element as well.
Answer:
D. 76%
Explanation:
Percent yield=actual/theoretical * 100
38/50 * 100 = 76%
