Answer:
This is an example of chemical change because the Kool aid dissolved and turned the water red
Answer:
They all have the same number of protons but different numbers of neutrons.
Explanation:
These are called isotopes. Isotopy is the existence of two or more atoms of the same element having the same atomic number but different mass numbers due to the differences in the number of neutrons in their various nuclei.
The atomic number is the number of protons in an atom. For a neutral atom, it is the same as the number of electrons.
The mass number is the number of protons and neutrons in an atom.
silicon-28 (28Si)
silicon-29 (29Si)
silicon-30 (30Si)
All of these isotopes have an atomic number of 16
Now let us chech for the neutrons:
Number of neutrons = mass number - atomic number:
for silicon-28 (28Si) : 28-16 = 12 neutrons
silicon-29 (29Si)
: 29-16 = 13 neutrons
silicon-30 (30Si): 20-16 = 14 neutrons.
Answer:
1. The change in energy is 60KJ or 6.0 × 10^1 KJ
2. Endothermic reaction
Explanation:
The Enthalpy (ΔU) for the mixture is given as 215kJ and the workdone (W) on the mixture is - 155KJ. Hence, the change in the energy (ΔH) ofthe mixture is computed using the equation below:
ΔH = ΔU + w
Where,
ΔH= Change in energy
ΔU= Enthalpy change
W= workdone
Therefore ΔH is:
ΔH= 215 kJ + (-155Kj)
ΔH= 60 KJ
Therefore, the change in energy is 60KJ or 6.0 × 10^1 KJ
The value is positive so it is an endothermic reaction.
An endothermic reaction happens when the energy used to break the bonds in the reactants is higher than the energy given out when bonds are formed in the products. This means that the entire reaction takes in energy, hence there is a temperature decrease in the surroundings. Endothermic reactions cannot happen spontaneously. Work is usually done in order to get these reactions to occur. When endothermic reactions absorb energy, a temperature drop is measured by the reaction.
Answer:
Explanation:
Step 1: Given data
- Molarity of the HF solution (M): 0.500 M
- Volume of the solution (V): 750.0 mL
Step 2: Convert "V" to liters
We will use the conversion factor 1 L = 1000 mL.
750.0 mL × 1 L/1000 mL = 0.7500 L
Step 3: Calculate the moles of HF
We will use the following expression.
n = M × V
n = 0.500 mol/L × 0.7500 L = 0.375 mol
Step 4: Calculate the atoms of F in 0.375 moles of HF
We will use the following relationships:
- 1 mole of HF contains 1 mole of atoms of F.
- 1 mole of atoms of F contains 6.02 × 10²³ atoms of F (Avogadro's number).
