Answer:
1. an educated guess
2. data
3. what changes in experiment
4. what stays the same in both groups
5. the group where nothing changes, normal
6. group with independent variable, what's being tested
Density = mass/volume = 800/200 =4 g/cm^3
The correct answer is:
A positively charged nucleus is surrounded by one or more negatively charged electrons
The explanation:
when:
proton is a positively charged elementary particle that is a fundamental constituent of all atomic nuclei.
neutron is a subatomic particle found in the nucleus of every atom except that of simple hydrogen. The particle derives its name from the fact that it has no electrical charge
electron is a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom .
so, , there are positively charged protons and zero-charged neutrons in the nucleus of an atom. Therefore, the nucleus is positively charged, Surrounding the nucleus, the electrons have negative charge.
Thus, the correct answer is (3): A positively charged nucleus is surrounded by one or more negatively charged electrons is correct.
Answer:
We need 41.2 L of propane
Explanation:
Step 1: Data given
volume of H2O = 165 L
Step 2: The balanced equation
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
Step 3: Calculate moles of H2O
1 mol = 22.4 L
165 L = 7.37 moles
Step 4: Calculate moles of propane
For 1 mol C3H8 we need 5 moles O2 to produce 3 moles CO2 and 4 moles H2O
For 7.37 moles H2O we need 7.37/4 = 1.84 moles propane
Step 5: Calculate volume of propane
1 mol = 22.4 L
1.84 moles = 41.2 L
We need 41.2 L of propane
The mole fraction is calculated using the formula:
mole fraction of component A = # of moles of component A / # of total moles of the solution.
A) number of moles of ethanol
To calculate the number of moles of ethanol, you need its density, which will permit you to determine the mass of the 10.00 ml, and then convert into moles using the molar mass of ethanol.
The normal density of ethanol is 0.789 g/ml
density = mass / volume => mass = density * volume = 0.789 g/ml * 10.00 ml = 7.890 g
Molar mass of ethanol = 46.07 g/mol
number of moles = mass / molar mass = 7.890g / 46.07 g/mol = 0.1713 mol
B) number of moles of water
density of water = 1.00 g/mol
mass of water = density * volume = 1.00 g/mol * 2.00 ml = 2.00 g
number of moles of water = mass / molar mass = 2.00 g / 18.0 g/mol = 0.111 mol
C) mole fraction
mole fraction of ethanol = number of moles of ethanol / number of moles of solution
number of moles of ethanol = 0.1713 / (0.1713 + 0.111) = 0.1713 / 0.2824 = 0.607
Answer: 0.607
The volume of the final solution may be calculated by adding the volume of the two components. This is 10.00 ml of ethanol + 2.00 ml of water makes 12.00 ml of solution.
It is not clear what the second question is meant for. Some context is missing. If you know density and you know maqss (or can calculate the mass from other data) you do not need to measure the volume.
