Answer:
116 g
Explanation:
From the question given above, the following data were obtained:
Number of mole of calcium = 2.9 moles
Mass of calcium =.?
The mole and mass of a substance are related according to the following formula:
Mole = mass / molar mass
With the above formula, we can obtain the mass of calcium. This can be obtained as follow:
Number of mole of calcium = 2.9 moles
Molar mass of calcium = 40 g/mol
Mass of calcium =.?
Mole = mass / molar mass
2.9 = mass of calcium / 40
Cross multiply
Mass of calcium = 2.9 × 40
Mass of calcium = 116 g
Therefore, the mass of 2.9 moles of calcium is 116 g.
Answer:
A machine have 75% efficiency means 25% of efficiency has been lost due to friction and a machine can work 75% only.
Every atom tends to form configuration of noble gas , with the 8 electrons in valence shell.
You start by diving each quantity given by the atomic wight of each element:
Phosphorus (P) 
Hydrogen (H) 
Then you divide by the lowest number:
for phosphorus
for hydrogen
So the empirical formula will be:
Well partly yes because air pollution can happen when we burn fossil fuels, it can happen when we use vehicles and household/farming chemicals can cause air pollution so yes it is caused by humans
