Answer: A
Explanation: mechanical weathering —Water gets into the cracks, freezes and expands making the cracks bigger. When there is thawing, the ice melts into water and more water gets into the rock. Freezing can happen again and the cracks get bigger.
Answer:
There will be produced:
2.97 moles HMnO4
4.45 moles Pb(NO3)2
2.97 moles H2O
Explanation:
Step 1: Data given
Manganese(II) oxide = MnO2
lead(IV) oxide = PbO2
nitric acid = HNO3
Moles of HNO3 = 8.90 moles
Step 2: The balanced equation
2MnO2 + 3PbO2 + 6HNO3 → 2HMnO4 + 3Pb(NO3)2 + 2H2O
Step 3: Calculate moles of reactants and products
For 2 moles MnO2 we need 3 moles PbO2 and 6 moles HNO3 to produce 2 moles HMnO4, 3 moles Pb(NO3)2 and 2 moles of water
For 8.90 moles of HNO3, there will react:
8.90 / 3 = 2.97 moles MnO2
8.90 / 2 = 4.45 moles PbO2
There will be produced:
8.90/3 = 2.97 moles HMnO4
8.90/2 = 4.45 moles Pb(NO3)2
8.90 / 3 = 2.97 moles H2O
Answer:
36.5 mol
Explanation:
The vapor pressure of a solution of a non volatile solute in water is given by Raoult´s law:
P H₂O = χ H₂O x P⁰ H₂O
where χ H₂O is the mole fraction of water in the solution and P⁰ H₂O
In the turn the mole fraction is given by
χ H₂O = mol H₂O / total # moles = mol H₂O /ntot
Thus
P H₂O = mole H₂O / n tot x P⁰ H₂0
now the mol of H₂O is equal n tot - 6 mol solute
Plugging the values given in the question and solving the resultant equation
19.8 torr = ( ntot - 6 ) x 23.7 torr / n tot
19.8 ntot = 23.7 ntot - 142.2
ntot = 36.5 ( rounded to 3 significant figures )
firm support that bears weight of microscope = base
