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 = 
Answer:
I am pretty sure the correct answer is a reproductive system
Explanation:
A column on the periodic table represents a period.
These are some of the variations observed across a period;
- Atomic radii decreases progressively from left to right due to the progressive increase in the nuclear charge without an attendant increase in the number of electronic shells.
- Ionization energy increases progressively from left to right due to decreasing atomic radii.
- Electronegativity increases from left to right.
- Electropositivity decreases across a period.
They are all in forest climax means forest
Why is paraffin oil constantly stirred to determine the melting point of benzene acid?
- Paraffin oil is used for determination of boiling point and melting point for the following reasons: It has a very high boiling point and so it can be used to maintain high temperatures in the boiling and melting point apparatus without loss of the substance.
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