Answer:
The new acceleration becomes twice the pervious acceleration.
Explanation:
Given that,
Mass of the rock, m = 3 kg
Force, F = 1 N
We know that the force acting on an object is given by :
F = ma
a is acceleration of the rock
Put m = 3 kg and F = 1N,

If the force is doubled, F' = 2 N
So,
F'=ma'

So, the new acceleration becomes twice the initial acceleration.
<u>Answer:</u> The chemical reaction for the synthesis reaction is given below.
<u>Explanation:</u>
Synthesis reaction is defined as a chemical reaction in which two small chemical substances combine together to form a single compound. The general equation for this chemical reaction follows:

For the reaction of calcium and oxygen combining together to form calcium oxide, the equation follows:

By Stoichiometry,
2 moles of calcium element combines together with 1 mole of oxygen gas to produce 2 moles of calcium oxide.
Hence, the chemical equation for the reaction is given above.
Answer: 17) d. 
18. c. The empirical formula of a compound can be twice the molecular formula.
Explanation:
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
To calculate the molecular formula, we need to find the valency which is multiplied by each element to get the molecular formula.
The equation used to calculate the valency is:

The empirical mass can be calculated from empirical formula and molar mass must be known.
17. Thus the empirical formula of
should be 
18. The molecular formula will either be same as empirical formula or is a whole number multiple of empirical formula. Thus the empirical formula of a compound can never be twice the molecular formula.
Answer: B,C,D
Explanation: Who ever reads this have a great day and stay safe :}