1 Na = 23 g/mol
1 mole of Na atom contain an Avogadro Number of atoms .
23g of Na Na atom contain 6.02 * 10²³ atoms.
175 g of Na will contain: 175 * <span>6.02 * 10²³ / 23
</span>
≈ 4.580 * 10²⁴ atoms of Na.
B) they have no charges and are inside an atom.*
Answer:
D. These elements have properties of both metals and nonmetals.
Explanation:
It can be concluded that the elements have properties of both metals and non-metals.
The elements that borders the ones described are both metals and non-metals. Most of these elements can be classified as metalloids.
On the periodic table, the elements around this region have properties of both metals and non-metals at certain temperature and pressure conditions.
Atoms, the main constituents of matter, consist of positively charged protons and neutral neutrons within a nucleus which are surrounded by a sea of electrons that sit in distinct shells. The electrons on the outer shell are known as valence electrons. The valence can be descibed as the smaller number of electrons an atom has to borrow or to lend, the greater the activity.
The answer is B.
Your question is not complete as you have omitted some significant values in the question. Please let me assume this to be your question;
QUESTION;
Understanding the enthalpy definition=
Measurements show that the enthalpy of a mixture of gaseous reactants increases by 125.kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -71.kJ of work is done on the mixture during the reaction. Calculate the change in enthalpy of the gas mixture during the reaction and determine if the reaction is endothermic or exothermic.
ANSWER: The change in enthalpy of the gas mixture during the reaction is 54.kJ
The reaction is endothermic.
EXPLANATION: Enthalpy is the heat change in a system.
To calculate enthalpy we use the formula below;
H = E + PV
H is the enthalpy
E is the energy used in the reaction
PV is the product of pressure and volume which is refered to as the work done in the system
Using the equation above
H = 125 + (-71) = 54.kJ
An endothermic reaction is a type of reaction where heat is gained by the system from it's environment, and the enthalpy of such system is positive. While an Exothermic reaction is a type of reaction where heat is lost by the system to it's environment, and the enthalpy of such system is negative.
Because our enthalpy value is positive, this is an endothermic reaction.
