Answer:
a)The total number of platinum atoms are 
.
b)The radius of a Pt atom is 138.7 pm.
Explanation:
a) Let the total number of platinum atoms be x
And mass of x atoms of platinum be m
Edge length of platinum cube ,s= 1.0 cm
Volume of the cube = 
Density of the platinum cube = 
Mass = Density × Volume
Mass of an atom of platinum = 
b) If only 74 percent of the space inside the cube is taken up by Pt atoms.
Volume occupied by platinum atoms = 74% of
Volume occupied by 
atoms is
.
The radius of a Pt atom is 138.7 pm.
Answer:
A balanced chemical equation must always include coefficients on every reactant and product.
Explanation:
<u>A balanced chemical equation does not need to include coefficients on every reactant and product.</u>
For example, below is a balanced chemical equation in which the reactants and the products have no coefficients whatsoever:
NaOH(aq) + HCl (aq) -----> NaCl (s) + H2O (l)
<em>Of course, a properly written chemical equation must include the states of matter of all the substances in the reaction and the number of atoms of each element must balance both in the reactant and product sides of the equation. Generally, a balanced chemical equation must obey the law of conservation of matter which opines that matter can neither be created nor destroyed but can only be converted from one form to another. </em>
Hence, that a balanced chemical equation must always include coefficients on every reactant and product is not true.
#6: The living organisms in an ecosystem can be divided into three categories: producers, consumers and decomposers. They are all important parts of an ecosystem.
#7: Nature has its own recycling system: a group of organisms called decomposers. Decomposers feed on dead things: dead plant materials such as leaf litter and wood, animal carcasses, and feces. They perform a valuable service as Earth's cleanup crew
HOPE THIS HELPS
A quantitative observation is an observation obtained from using instruments or tools such as balances, rulers, beakers and thermometers. The results here are measurable. The opposite is called the quantitative observations where the senses are used to see a result.
27 km = 27000m. Time = distance/speed = 27000/3x10^8 = 9x10^-5 s.
