Answer : The balanced chemical equation will be:
(i) 
(ii) 
Explanation :
Balanced chemical equation : It is defined as the equation in which total number of individual atoms on the reactant side is equal to the total number of individual atoms on product side.
Part (i):
The balanced chemical equation will be:

This reaction is a single displacement reaction in which most reactive element (potassium) displaces the least reactive element (hydrogen) form their solution.
Part (ii):
The balanced chemical equation will be:

This reaction is a single displacement reaction in which most reactive element (zinc) displaces the least reactive element (magnesium) form their solution.
Answer:
0.0069
Explanation:
When converting between scientific notation try to remember that moving the decimal place to the left is positve and to the right is negative
Since you are changing from scientific to standard you will need to move to the left from the decimal point, making your answer 0.0069
Answer:
A. is alloyed with carbon and chromium to make stainless steel.
Explanation:
Steel is an alloy formed mainly of iron and carbon but some other metals like chromium are also added in little amounts.
Is steel, the percentage of iron and carbon together is about 90% and the rest metals fall in the 10% part.
Although the cost of steel is low, it has a very high tensile strength and that's why it is used in tools, ships, buildings, trains and in various types of infrastructures.
If the results of the experiment on repeating are not same, it shows the results are not standard, there are some factors, which are not constant