Number 18 is correct, number 19 is the particles speed up and the substance expands, and number 20 is decrease in volume
Number of moles = volume / (molar volume)
Molar volume at stp = 22.4 dm^3
Volume = no of moles × molar volume
= 0.987 × 22.4
= 22.1088 dm^3
= 22108.8 cm^3
Hope it helped!
Hydrogen. Covalent bonds occur within each linear strand and strongly bond the bases, sugars, and phosphate groups (both within each component and between components). Hydrogen bonds occur between the two strands and involve a base from one strand with a base from the second in complementary pairing.
You forgot to include the known characteristics of the solution.
I searched them and copy here:
volume: 1.000 liter
M = 0.0190 M
Now, you can start with the definition of mass percent.
mass percent = (grams of solute / grams of solution) * 100
grams of solute are obtained from the molar concentration:
M = (number of moles of solute) / (volume of solution in liters)
where number of moles = (grams) / (molar mass)
=> M = (grams of solute / molar mass of solute) / (volume of solution in liters)
=> grams of solute = M * (volume of solution in liters) * (molar mass of solute)
And density = (kg of solution / volume of solution in liters) =>
kg of solution = density * volume of solution in liters
grams of solution = density * (volume of solution in liters) * 1000 g/kg
=> mass percent = M * (volume of solution in liters) * (molar mass) / (density * volume of solution in liters * 1000 g/ kg) * 100
=> mass percent = M * molar mass * 10 / density
now replace the values known:
M = 0.0190 mol / liter
density = 1,000 kg / liter
molar mass of Ba(NO3)2 = 137.327 g/mol + 2*14.007 g/mol + 2*3*15.999 g/mol = 256.335 g/mol
=> mass percent = 0.0190 mol/liter * 256.335 g/mol * 10 kg/ g / (1.000 kg/liter)
=> mass percent = 48.7%
for one you could do a bell, ringing noise, then say someone rang it.
For two you could do tunnel, echoing, then say someone yelled and it echoed.
for three you could do a bowl, ringing, spoon hitting it
hope i could help
