10g
Explanation:
Box 1, Mass of A = 10g
Box 2, Mass of B = 5g
Box 3, = 1A + 1B
Unknown:
Mass of B that would combine with mass of 20g of A
Solution:
Mass ratio of A to B:
= mass ratio
= mass ratio
The mass ratio of A to B = 2: 1
Now, number of B that will combine with 20g of A;
= mass ratio
= 
Mass of B = 10g
10g of B would combine with 20g of A
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2 C₃H₇OH (l) + 9 O₂ (g) → 6 CO₂ (g) + 8 H₂O (g)
Explanation:
To balance the chemical equation the number of atoms of each element entering the reaction have to be equal to the number of atoms of each element leaving the reaction, in order to conserve the mass.
Bellow we have the balanced chemical equation of the complete combustion of C₃H₇OH:
C₃H₇OH (l) + (9/2) O₂ (g) → 3 CO₂ (g) + 4 H₂O (g)
to have integer coefficients we multiply the reaction with 2:
2 C₃H₇OH (l) + 9 O₂ (g) → 6 CO₂ (g) + 8 H₂O (g)
where:
(l) - liquid
(g) - gaseous
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Answer: 72 grams of
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number
of particles.
To calculate the number of moles, we use the equation:

Putting in the values we get:


According to stoichiometry:
1 mole of
requires 5 moles of oxygen
0.45 moles of
require=
moles of oxygen
Mass of 
72 grams of
are needed to completely burn 19.7 g 
Answer:
Precipitation
Explanation:
In the water cycle, water experiences different phase changes from one state to another in nature.
The cycling affords water to in solid, liquid and the vapor form.
From the cycle show, W represents precipitation.
- During precipitation, water in the atmosphere begins to fall.
- U is evaporation
- X is transpiration.
- V is the condensation.