Answer:
See Explanation
Explanation:
1) Let us recall that;
Mass number = number of protons + number of neutrons
Where;
Number of protons = ?
Number of neutrons =20
Mass number =39
Number of protons = mass number - number of neutrons
Mass of protons =39 - 20= 19 protons
2) Atomic number = 13
Number of neutrons =14
Then the mass number =13 +14 =27
The symbol of the element is 27X13
The number of protons= the number of electrons =13
The atomic number is the same as the proton number =13
explain what you understand by valency, give examples
Answer:
Valency is defined as the number of hydrogen atoms which combine directly or indirectly with one atom of an element.
Example:
One atom of nitrogen combines with three atoms of hydrogen to form ammonia gas. So, the valency of nitrogen is 3.
Which of the following correctly describes the role of the mouth in the digestive system?
The mouth acts like a muscular bag by churning the food and producing enzymes that aid in chemical digestion.
The mouth produces all of the enzymes needed for digestion and these enzymes are swallowed, which moves them through the digestive tract.
The mouth begins the process of digestion by mechanically breaking food into smaller pieces.
The mouth performs the peristalsis that pushes food through the rest of the digestive system.
Answer:
The mouth begins the process of digestion by mechanically breaking food into smaller pieces.
Explanation:
Digestion is a crucial process that involves the break down of complex food molecules into simpler ones that are assimilable by the body. The process of digestion in humans, for example, is said to begin in the MOUTH where the food enters through.
The mouth via the use of teeth helps the initially break down the food particles using mechanical/physical method. This further helps the break down of the food into tiny particles before they are acted on enzymatically.
A gas initially has a volume of 300. mL at a pressure of 1.0 atm, what will the
new volume be if the pressure is doubled? (assume constant temperature)
Which represents a balanced nuclear equation?
Describe the trends in properties of chlorides across period 3 .Their formula .Their state .Their volatility .Their structure .The ph of aqueous chloride solution
Answer:
See explanation
Explanation:
Period 3 elements include; Na, Mg, Al, Si, P,S,Cl and Ar
Across the period, the chlorides of the elements change from solid to gas. The chlorides of metals are solid while the chlorides of non metals are gaseous.
Also, the chlorides become more volatile across the period. The formulas of the chlorides change from MCl to MCl2 to MCl3 to MCl4, MCl5 and MCl6 respectively across the period where M is a period 3 element.
The pH of the solutions of chlorides of period 3 elements change from neutral to acidic across the period. The pH of the chlorides of metals are neutral while the chlorides of the nonmetals usually yield acid solutions.
What is the amount of sodium hydroxide, NaOH, in 4.6 g? Use the values given for
the atomic mass of Na, H, and O.
6
Na = 22.989 770 u
H = 1.007 94u
0 = 15.99944
9
a) 0.19 mol
12
b) 0.12 mol
15
c) 1.8 x 102 mol
d) 0.20 mol
Answer: 0.12 Mol
Explanation: Molecular mass of NaOH is = 39,997 g/mol which is Atomic mass of Na + Atomic Mass of H + Atomic mass of O
4.6g / 39.997g/mol = 0.12 mol
A seais usually defined as A.A body of freshwater that is not connected to the ocean B. A body of freshwater that is connected to the ocean C. A body of salt water that is not connected to the ocean D. Body of salt water that is connected to the ocean
Answer:
D. Body of salt water that is connected to the ocean
Explanation:
An ocean is a body of salt water which covers approximately 70% of the Earth's surface. About 97% of the Earth's water is comprised of ocean and as such it is the most prominent and defined feature of the Earth. There are basically four (4) categories of an oceanic basin and these are;
1. The Pacific ocean.
2. The Artic ocean.
3. The Atlantic ocean.
4. The Indian ocean.
A sea is usually defined as a body of salt water that is connected to the ocean and are surrounded (enclosed) by land partially.
Basically, a sea is formed where a land and an ocean meet and as a result, an ocean is usually bigger than a sea.
Some examples of seas around the world are Red sea, Mediterranean sea, Sargasso sea, Caribbean sea, Baltic sea, Caspian sea, Chuckchi sea, etc.
Answer:
Yes The Anwer is D Hope This Help:)
Can you please help me with this?
What happens with the evaporation of raindrops in the atmosphere?
Answer:
they become water vapor and after that, they become a type of precipitation
What is Rin the ideal gas law equation?
A. The kinetic energy of the gas
B. The molar mass of the gas
C. The number of moles of the gas
D. The ideal gas constant
Answer:
R is the ideal gas constant
Check all that indicate a chemical change. Check all that apply. Group of answer choices aqueous solutions of silver nitrate and sodium chloride turn cloudy after mixing aqueous solutions of hydrochloric acid and sodium hydrogen carbonate produces bubbles on mixing Sodium hydroxide is mixed with water and the container feels warmer Water is added to orange juice is the color becomes lighter. No answer text provided. ice melts on a bench top at room temperature
Answer:
aqueous solutions of silver nitrate and sodium chloride turn cloudy after mixing aqueous solutions of hydrochloric acid and sodium hydrogen carbonate produces bubbles on mixing Sodium hydroxide is mixed with water and the container feels warmer
Explanation:
A chemical change involves the formation of new substances. Also heat is absorbed or released in a chemical change. Another name for a chemical change is a chemical reaction.
In the first case, a reaction of the sort;
AgNO3(aq) + NaCl(aq) ---> AgCl(s) + NaNO3(aq)
The cloudy solution is due to the formation of AgCl precipitate.
In the second case, a reaction of the sort;
HCl(aq) + NaHCO3(aq) ---> NaCl(aq) + CO2(g) + H2O(l)
The gas evolved is due to the formation of CO2 in the process. Heat is also evolved showing that it is a chemical change.
where is reverse osmosis used
Answer:
Reverse osmosis systems find frequent use in the following: Boiler feed-water treatment: used to reduce solids content of waters prior to feeding into boilers for power generation or otherwise.
Explanation:
Help! Locks at 12
Given the balanced equation representing a nuclear reaction:
Which particle is represented by X?
Answer is #4 (neutrons)
Explanation:
Total mass before the reaction is 236 amu. The total mass of the two elements is 233 amu. This means that there are 3 amus carried by element X. Looking at the total atomic number of the two elements after reaction, it's 92, the same as the one at the beginning. This means that element X has zero atomic number, which could only be a neutron.
Answer: is 4
Explanation:
I was doing the same one
A mixture of gases with a pressure of 900 mm Hg contains 20% of oxygen and 80% of nitrogen by volumeWhat is the partial pressure of the oxygen gas in the mixture?
A-45mmHg
B-180mmHg
C-210 mmHg
D-320 mmHg
Answer:
180 mmHg
Explanation:
Total volume of gases = 20% + 80%= 100%
Total pressure of gases = 900 mm Hg
Note that partial pressure of a gas = mole fraction × total pressure
Mole fraction of oxygen = 20/100
Hence partial pressure of oxygen= 20/100 × 900 mm Hg
partial pressure of oxygen= 180 mmHg
NEED HELP!! See picture for question!
Answer: The answer is A.
two types of fine chemical
Answer:
Flavors and fragrances
if 5.0g zinc reacts with 10.0 g hci to produce h2 gas and znci2 according to the following equation zn=2hci znci2 + h2 what is the limiting reactant and how many grams of h2 will be produced
Answer: The mass of [tex]H_2[/tex] produced is 0.153 g
Explanation:
The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)
For zinc:Given mass of zinc = 5.0 g
Molar mass of zinc = 65.38 g/mol
Putting values in equation 1, we get:
[tex]\text{Moles of zinc}=\frac{5.0g}{65.38g/mol}=0.0765mol[/tex]
For HCl:Given mass of HCl = 10.0 g
Molar mass of HCl = 36.46 g/mol
Putting values in equation 1, we get:
[tex]\text{Moles of HCl}=\frac{10.0g}{36.46g/mol}=0.274mol[/tex]
The given chemical equation follows:
[tex]Zn+2HCl\rightarrow ZnCl_2+H_2[/tex]
By stoichiometry of the reaction:
If 1 mole of zinc reacts with 2 moles of HCl
So, 0.0765 moles of zinc will react with = [tex]\frac{2}{1}\times 0.0765=0.153mol[/tex] of HCl
As the given amount of HCl is more than the required amount. Thus, it is present in excess and is considered as an excess reagent.
Thus, zinc is considered a limiting reagent because it limits the formation of the product.
By the stoichiometry of the reaction:
If 1 mole of zinc produces 1 mole of [tex]H_2[/tex]
So, 0.0765 moles of zinc will produce = [tex]\frac{1}{1}\times 0.0765=0.0765mol[/tex] of [tex]H_2[/tex]
We know, molar mass of [tex]H_2[/tex] = 2 g/mol
Putting values in above equation, we get:
[tex]\text{Mass of }H_2=(0.0765mol\times 2g/mol)=0.153g[/tex]
Hence, the mass of [tex]H_2[/tex] produced is 0.153 g
i need help asap please :) it says to “identify the reactants.”
the options are
A: Carbon Dioxide and water
B: Glucose and oxygen
C: sunlight and chlorophyll
The reactants are A: Carbon Dioxide and water
how many types of kinetic energies are there? is it 4 or 5 types?
Calculate the standard free energy change, ΔG°, for the following at 25 °C:
MgO(s) + C(graphite) ® Mg(s) + CO(g)
ΔH° = 491.18 kJ ΔS° = 197.67 J/K
Answer:
Explanation:
here is your answer:
write the recation of formation of ions by fluorine and potassium
Answer: The reaction of formation of ions by fluorine and potassium is [tex]K^{+} + F^{-} \rightarrow KF[/tex].
Explanation:
Atomic number of potassium is 19 and its electronic distribution is 2, 8, 8, 1. So, in order to attain stability it needs to lose 1 electron due to which it forms [tex]K^{+}[/tex] ion.
Atomic number of fluorine is 9 and its electronic distribution is 2, 7. In order to attain stability it needs to gain one electron and hence forms [tex]F^{-}[/tex] ion.
Therefore, when both these ions come in contact with each other then it leads to the formation of KF compound.
The reaction equation for this is as follows.
[tex]K^{+} + F^{-} \rightarrow KF[/tex]
Thus, we can conclude that the reaction of formation of ions by fluorine and potassium is [tex]K^{+} + F^{-} \rightarrow KF[/tex].
Choose all the answers that apply.
Plasma is made of _____.
ions
clumped atoms
neutral atoms
free electrons
free protons
Answer:
neutral atoms
Explanation:
An inflated balloon contains X air molecules.After some time the volume of the balloon is found to be the half at the same temperature and pressure when a few air molecules are expelled out. a)How many molecules will be there in the balloon now? b) Which is the gas law associated with this?
Answer:
See explanation
Explanation:
According to Avogadro's law, the volume of a given mass of gas is directly proportional to the number of molecules of gas present at constant temperature and pressure.
Hence; V1/n1 = V2/n2
The implication of this is, if there were X molecules present and the volume of the balloon is halved, the number of molecules of gas present is also halved. So, we now have X/2 number of gas molecules present in the balloon.
This is in accordance with the statement of Avogadro's law.
Why do we not see a solar and lunar eclipse every lunar cycle?
Answer:
Explanation: We don't see lunar eclipses every cycle because the Moon's orbit is tilted five degrees from Earth's orbit around the Sun. And when an eclipse occurs the earth passes directly between Sun and Moon.
11. In the diagram below, what will allow more solute to be dissolved in the
solvent?
Please help !!!Is this Lewis dot structure correct? Check whether each atom has an octet and whether the total electrons in the structure match the total valence
electrons of the elements. There MUST be a clear yes/no and some evidence of work in your answer
Answer:
The Lewis dot structure is not correct
Explanation:
Each atom ought to be surrounded by eight electrons or two electrons according to the octet rule. We now need to closely examine the structure to see if it fits into this description.
All the atoms in the molecule have the correct valence except the hydrogen which is directly attached to the oxygen.
The positive charge ought to mean that more than two bonds were formed between hydrogen and oxygen which is clearly not the case here.
Thus, the hydrogen atom attached directly to oxygen does not display the correct valence.
