Explanation:tr
a) Molar mass of HF = 20 g/mol
Atomic mass of hydrogen = 1 g/mol
Atomic mass of fluorine = 19 g/mol
Percentage of an element in a compound:
Percentage of fluorine:
Percentage of hydrogen:
b) Mass of hydrogen in 50 grams of HF sample.
Moles of HF = 
1 mole of HF has 1 mole of hydrogen atom.
Then 2.5 moles of HF will have:
of hydrogen atom.
Mass of 2.5 moles of hydrogen atom:
1 g/mol × 2.5 mol = 2.5 g
2.5 grams of hydrogen would be present in a 50 g sample of this compound.
c) As we solved in part (a) that HF molecules has 5% of hydrogen by mass.
Then mass of hydrogen in 50 grams of HF compound we will have :
5% of 50 grams of HF = 
For the purpose we will here use the ideal gas law:
p×V=n×R×T
V= ?
n = 0.5 moleT= 273.15 K (at STP)
p= 101.325 kPa (at STP)
R is universal gas constant, and its value is 8.314 J/mol×K
Now when we have all necessary date we can calculate the number of moles:
V=nxRxT/p
V=0.5x8.314x273.15/101.325= 11.2 L = 11200 mL
Answer: D.
The density of magnesium will be 1.74 g/cm³ if 23.5 g of magnesium occupies 13.5 cm³
<h3>What is Density ?</h3>
Density is the measurement of how tightly a material is packed together.
It is defined as the mass per unit volume.
Given ;
- Mass = 23.5 g
- Volume = 13.5 cm³
Formula to calculate density ;
Density = mass / volume
=23.5 / 13.5 = 1.74 g/cm³
Hence, the density of magnesium will be 1.74 g/cm³ if 23.5 g of magnesium occupies 13.5 cm³.
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Answer:
An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. It has multiple applications in research and engineering, with common usage in hydroponics, aquaculture, aquaponics, and freshwater systems to monitor the amount of nutrients, salts or impurities in the water.
There are 3 experiments which helps to under water evaporation system.
- Both the temperature of the air surrounding the water and the rate of evaporation increased.
- In the second experiment, we observed an increase in air flow around the water, and this time, the rate of evaporation increased as well.
- In the third and final experiment, we observed an increase in the amount of light in the room, and this time, the rate of evaporation increased as well.
- Because the kinetic energy of a substance can be measured by its temperature, increasing in the temperature or kinetic energy of the air around water will also increase the kinetic energy of the water, which will increase the rate of evaporation.
- It's crucial to have good air flow since it drives water droplets in the air away from you, reducing the amount of humidity in the region. Because there will then be space for the evaporated air or space for the evaporated water to flow into the air, it will then be simpler for the water to really evaporate.
- Water in the presence of sunlight is given extra energy, which increases evaporation.
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