0.008 ÷ 51.3 = 0.0002
Sig Figs
1
0.0002
Decimals
4
0.0002
Scientific Notation
2 × 10-4
E-Notation
2e-4
Words
zero point zero zero zero two
I HOPE I HELP
Answer:
The element is strontium and the number of neutrons it have is 51.
Explanation:
Based on the given information, the ionic compound is,
XCl₂ ⇔ X₂⁺ + 2Cl⁻
X2+ is the ion of the mentioned element
As mentioned in the given question, the number of electrons of the element X is 36 and as seen from the reaction the charge present on the ion is +2. Now the atomic number will be,
No. of electrons = atomic number - charge
36 = atomic number - 2
Atomic number = 38
Based on the periodic table, the atomic number 38 is for strontium element, and the sign of strontium is Sr. Hence, the element X is Sr.
Now based on the given information, the mass number of the element is 89. Now the no. of neutrons will be,
No. of neutrons = mass number - atomic number
= 89 - 38
= 51 neutrons.
Answer: Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color chage, formation of a precipitate, formation of a gas, odor change, temperature change.
The starting material or materials for a chemical reaction are referred to as the reactants. The substance or substances produced from a chemical reaction are called products. Sometimes a secondary product, a byproduct, can also be created at the same time as the desired product(s).
Not every chemical reaction occurs in the same way. There are different types of chemical reactions, including synthesis reactions, decomposition reactions, and displacement reactions. In this experiment, a decomposition reaction takes place. During a decomposition reaction, a compound breaks apart into two or more products. Most decomposition reactions need an outside source of energy in order to take place.
Hydrogen peroxide is not a very stable compound, so it slowly decomposes into water and oxygen gas under normal conditions. In this reaction, yeast is used as a catalyst. A catalyst is a substance that helps to change the rate of a reaction. During the reaction, the catalyst is not consumed. As a result, the yeast makes the reaction occur much faster; it causes the hydrogen peroxide to break down and release the oxygen gas much faster.
The soap is used to help us “see” the reaction. Bubbles of oxygen become trapped in the soap, creating foam. The reaction occurs so quickly, releasing so much gas and creating so much foam, that the foam begins to flow out of the bottle. The result of this reaction looks like toothpaste being squeezed out of a tube.
In addition, the bottle will feel warm to the touch because the reaction is exothermic. An exothermic reaction or process is one that gives off energy. In contrast, an endothermic reaction or process is one that requires or absorbs energy.
HYPOTHESIS
uAdding yeast to hydrogen peroxide
will cause the hydrogen peroxide to
decompose quickly into water and oxygen gas, creating foam as the gas becomes trapped in liquid dish soap and pushes upward out of the bottle.
FORMULAS & EQUATIONS
Hydrogen peroxide is a relatively clear liquid substance. It is soluble in water and is often sold as a mixture of H2O2 in water. The hydrogen peroxide used in this experiment is actually a 6% solution of H2O2 in water.
The chemical formula for hydrogen peroxide is H2O2.
Hydrogen peroxide naturally decomposes into water and oxygen gas. The reaction is shown by the following equation:
2H2O2 (aq)g2H2O (l) + O2 (g)
The rate of the reaction can be increased by introducing a catalyst. In this experiment, the catalyst is yeast. Yeast is a microorganism that is part of the fungi family. Therefore, in the equation below, the catalyst is indicated above the arrow.
yeast
2H2O2 (aq) g 2H2O (l) + O2 (g)
The hydrogen peroxide used in the experiment is
actually a mixture of water and hydrogen peroxide.
CONNECT TO THE YOU BE THE CHEMIST CHALLENGE
For additional background information, please review CEF’s Challenge study materials online at http://www.chemed.org/ybtc/challenge/study.aspx.
• Additional information on elements, compounds, and physical and chemical changes can be found in the Classification of Matter section of CEF’s Passport to Science Exploration: The Core of Chemistry.
• Additional information on chemical reactions can be found in the Chemical Reactions section of CEF’s Passport to Science Exploration: Chemistry
