Answer:
c) 9.03 x 10^23
Explanation:
find the molar mass of Al
Al is 27.0 grams
Then use that, to find the number of moles in Aluminum.
Then use Avogadro's number which is 6.02 * 10^23
After that, write all of that down with dimensional analysis.
40.5 g * 1 mol/ 27.0 g of Al * 6.02 x 10^23 / 1mol
As your final answer, you will get 9.03 * 10^23 atoms with sig figs.
Hope it helped!
Answer:
There are many reasons to examine human cells and tissues under the microscope. Medical and biological research is underpinned by knowledge of the normal structure and function of cells and tissues and the organs and structures that they make up. In the normal healthy state, the cells and other tissue elements are arranged in regular, recognizable patterns. Changes induced by a wide range of chemical and physical influences are reflected by alterations in the structure at a microscopic level, and many diseases are characterized by typical structural and chemical abnormalities that differ from the normal state. Identifying these changes and linking them to particular diseases is the basis of histopathology and cytopathology, important specializations of modern medicine. Microscopy plays an important part in haematology (the study of blood), microbiology (the study of microorganisms including parasites and viruses), and more broadly in the areas of biology, zoology, and botany. In all these disciplines, specimens are examined under a microscope.
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Answer : The mass of 
required is 18.238 grams.
Explanation : Given,
Mass of 
= 83.10 g
Molar mass of = 146 g/mole
Molar mass of = 256.52 g/mole
The balanced chemical reaction is,
First we have to determine the moles of .
Now we have to determine the moles of .
From the balanced chemical reaction we conclude that,
As, 8 moles of produced from 1 mole of
So, 0.569 moles of produced from 
mole of
Now we have to determine the mass of .
Therefore, the mass of required is 18.238 grams.
Answer: (2) decreasing the concentration of HCl(aq) to 0.1 M
Explanation: Rate of a reaction depends on following factors:
1. Size of the solute particles: If the reactant molecules are present in smaller size, surface of particles and decreasing the size increases the surface area of the solute particles. Hence, increasing the rate of a reaction.
2. Reactant concentration: The rate of the reaction is directly proportional to the concentration of reactants.
3. Temperature: Increasing the temperature increases the energy of the molecules and thus more molecules can react to give products and rate increases.
(1) Increasing the initial temperature to 25°C will increase the reaction rate.
(2) Decreasing the concentration of HCl(aq) to 0.1 M will decrease the reaction rate due to lesser concentration.
(3) Using 1.2 g of powdered Mg will increase the reaction rate due to large surface area.
(4) Using 2.4 g of Mg ribbon will increase the reaction rate due to high concentration of reactants.
