Answer:
Substances can change phase—often because of a temperature change. At low temperatures, most substances are solid; as the temperature increases, they become liquid; at higher temperatures still, they become gaseous.
The process of a solid becoming a liquid is called melting. (an older term that you may see sometimes is fusion). The opposite process, a liquid becoming a solid, is called solidification. For any pure substance, the temperature at which melting occurs—known as the melting point—is a characteristic of that substance. It requires energy for a solid to melt into a liquid. Every pure substance has a certain amount of energy it needs to change from a solid to a liquid. This amount is called the enthalpy of fusion (or heat of fusion) of the substance, represented as ΔHfus. Some ΔHfus values are listed in Table 10.2 “Enthalpies of Fusion for Various Substances”; it is assumed that these values are for the melting point of the substance. Note that the unit of ΔHfus is kilojoules per mole, so we need to know the quantity of material to know how much energy is involved. The ΔHfus is always tabulated as a positive number. However, it can be used for both the melting and the solidification processes as long as you keep in mind that melting is always endothermic (so ΔH will be positive), while solidification is always exothermic (so ΔH will be negative).
Table 10.2 Enthalpies of Fusion for Various Substances
Explanation:
The number of atoms in 259 g of C₁₂H₂₁O₉ is 45 x 10²³ oxygen.
<h3>What is molar mass?</h3>
The molar mass of many compounds can be calculated by dividing the mass of the compound by the number of moles of the compound.
Given the molar mass is 309.29 g/mol
Given weight= 259g
number of moles = mass / molar mass
259g / 309.29g/mol =0.837mol
1 mol contains 6.022 x 10²³ molecules
0.837 mol contain 6.022 x 1023 x 0.837 = 5.0 x 10²³ molecules
1 molecule of C₁₂H₂₁O₉ contains 9 oxygen atoms
5.0 x 10²³ molecules of C₁₂H₂₁O₉ contain 9x 5 x 10²³ oxygen atoms.
=45 x 10²³ oxygen atoms
Thus, the number of atoms in 259 g of C₁₂H₂₁O₉ is 45 x 10²³ oxygen atoms
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Answer:
They develop partially or fully inside the mother's body. They have long gestation periods. Which characteristic is common to all three groups of mammals? They are always endotherms.
Explanation:
Answer:
Change in height of the object
Explanation:
Change in height of the object
Since ,
We know potential energy can be written as mgh where
P.E. = mgh
M = mass ,
g = gravity constant
h = height
Kinetic energy can be written as 0.5 mv²
So , the Potential energy = kinetic energy
Then ,
velocity of object = √2 gh
Since g is a constant ,
Hence ,
Height of object will determine the velocity.
Answer:
0.333 M
Explanation:
Step 1: Write the balanced equation
2 HCl(aq) + Mg(OH)₂(aq) = MgCl₂(aq) + 2 H₂O(l)
Step 2: Calculate the reacting moles of Mg(OH)₂
25.00 mL of a 0.200 M magnesium hydroxide react. The reacting moles of Mg(OH)₂ are:
Step 3: Calculate the reacting moles of HCl
The molar ratio of HCl(aq) to Mg(OH)₂ is 2:1. The reacting moles of HCl are:
Step 4: Calculate the molarity of HCl