Answer: correct option is B. Energy is released by the reaction
Explanation:
The exothermic reactions are the reactions in which energy is released.The released energy can be in the form of heat or light.
Temperature of the surrounding also increases.
For example:
- Neutralization reaction between acid and base.
Above reaction takes place in the aqueous medium.After the reaction mixtures becomes hot.
- Burning of Magnesium ribbon
In above reaction energy is released in the form light.
C. 3.10 g, 3.20 g, 3.23 g
I came to this conclusion because:
A. 3 g, 4 g, 5 g, well these have 10 units between (0.1, .2, etc) so they are not the closest.
B. 3.0, 4.0, 5.0 just like above, they still have 10 units between
D. 3.0, 4.0, 5.0, 6.0 these numbers, just like in the previous two, have 10 units between, making them not precise or the closest option.
C is your answer because 3.10 - 3.23 are only 2 units apart. Making them the most precise.
Answer:
Oxygen, bromine, iron, helium
Explanation:
is defined as the standard enthalpy of formation. By definition, the standard enthalpy of formation is equal to 0 kJ/mol for the substances in their standard states, that is, at room temperature and 1 atm pressure.
Simply speaking, looking at the substances given, we need to understand whether their states agree with what we expect to see at standard conditions (e. g., sodium is a metal, fluorine is a gas, bromine is a liquid at standard conditions). Those are substances consisting of just one type of atoms.
- Firstly, oxygen is a gas at standard conditions and it is diatomic, so its .
- Although nitrogen is a gas at standard conditions, it is diatomic, so .
- Water is a liquid at standard conditions, however, it consists of two types of atoms, hydrogen and oxygen, so .
- Bromine is a liquid at standard conditions, so .
- Iron is a solid at standard conditions, it's a metal, so .
- Helium is a gas at standard conditions, it belongs to noble gases, so .
- Sulfur is a solid at room conditions, however, the conformation it has is and not , so .
B. The element nitrogen is made up only of nitrogen atoms.
Explanation:
Dalton stipulated , in his theory, that all the atoms of pure elements were identical. However different elements had different kinds of atoms that differ in their size and mass. The other stipulations of Dalton's theory were that atoms are the smallest unit of mass and were indivisible – this was later rebutted by advanced atomic theories .
Another major contribution by Dalton's theory is that chemical reactions involved the rearrangement of atoms observing the law of conservation of mass,