which is correct? not sure which is right

Answer:

A) number of electrons

Explanation:

A calcium atom has 20 electrons while a calcium ion has 18 electrons since it loses 2 electrons to form a stable octet structure. The formula of a calcium ion is Ca2+.

The number of protons does not change, neither do the number of neutrons. Atomic number is the proton number which is equals to the number of protons, hence B and C is wrong. Mass number is the number of protons and neutrons. Hence it doesnt change too and D is wrong.

Only the number of electrons change when an atom forms an ion.

Answer:

1. sublimation

2.melting

3.melting  

4.sublimation

Explanation:

melting is a process when solid changes to liquid

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state.

Answer:

Should be A

Explanation:

"Typical nonmetals have a dull, coloured or colourless appearance; are brittle when solid; are poor conductors of heat and electricity; and have acidic oxides." - Wikipedia

Answer:

b

Explanation:

it is right

Answer: The reaction of one mole of oxygen [tex](O_2)[/tex] releases 445 kJ of energy.

Explanation:

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and [tex]\Delta H[/tex] for the reaction comes out to be negative.

Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and [tex]\Delta H[/tex] for the reaction comes out to be positive.

[tex]CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(l)[/tex]  [tex]\Delta H=-890kJ[/tex]

on halving the reaction, enthalpy also becomes half

[tex]\frac{1}{2}CH_4(g)+O_2(g)\rightarrow \frac{1}{2}CO_2(g)+H_2O(l)[/tex]  [tex]\Delta H=-445kJ[/tex]

Thus The reaction of one mole of oxygen [tex](O_2)[/tex] releases 445 kJ of energy.

Answer: c

Explanation: an xray wave does have a higher frequency than an infrared wave.

Answer:

Explanation:c

Winds are always named from the direction it blows from

Uneven heating of Earth's surface,in turn,causes differences in air pressure at various locations. Heated air rises,creating an area of low pressure beneath. Cooler air descends, creating an area of high pressure

Answer:

Magnets stick to the fridge door because, underneath the paint, the door is made of steel. Magnets are attracted to certain metals, and if the attraction is strong enough they can hold on even when upside down. ... This means that a magnet will always be attracted to the door. But an iron nail does not have any magnetic properties. So it doesnt get attracted.

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A small magnet will stick to a refrigerator door, but a nail will not stick

because magnets attract certain types of metals.

Magnets have a strong magnetic field which is why it attracts metals such

as iron and steel. The refrigerator must have been made with iron or steel

which was why the magnet stuck to it.

Metals such as aluminium and copper aren't attracted by magnets which is

why the nails weren't attracted as a result of it being made with metals which magnets don't attract.

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Answer:

4.92 L

Explanation:

Rearrange ideal gas law and solve.

Change C to K.

- Hope that helps! Please let me know if you need further explanation.

Answer:

By using the speed of sound in water

Explanation:

(Which is about 1500 m/s in sea depending on the sea water density )

Answer:

B the density stays the same

Answer:

kii

Explanation:

Answer:

2.078x10^24

Explanation:

No. of atoms of chlorine = 3.45 x 6.022x 10 ^23 x 1

= 2.078x10^24

( to find no. of atoms of, heres the formula i was taught No. of atoms = no. of moles x Avogadros constant x no. of atoms in the formula of compound)

The biggest disadvantage of using nuclear power to produce electricity is the nuclear waste must be safely stored for many years.

Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from:

Nuclear reactions produces high amount of energy and many waste materials which are non degradable and will stay in the environment for the long time.

Hence, nuclear waste must be safely stored for many years.

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#SPJ2

Answer:

Do you still need this answer? If you do i can provide it for you still

Thank you

Answer:

increases

Explanation:

As the temperature of a fixed volume of a gas increases, the pressure will increase.

According to this law at constant volume of gas, pressure is directly proportional to the temperature of the gas and it is represented as:

P ∝ T.

It means that if pressure increases then temperature is also increases or if pressure decreases then temperature will also decreases.

So, pressure of the gas increases.

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Answer:

[tex]\large \boxed{\text{0.44 g}}[/tex]  

Explanation:

1. Calculate the molar mass of ammonia

1  N = 1 × 14.01    g = 14.01    g

3 H = 3 ×  1.008 g =  3.024     

                   TOTAL = 17.03   g

2. Calculate the mass of hydrogen

So, there are 3.024 g of H in17.03 g of NH₃.

The conversion factor is either

[tex]\dfrac{\text{3.024 g H}}{\text{17.03 g NH}_{3}} \text{ or } \dfrac{\text{17.03 g NH}_{3}}{\text{3.024 g H}}[/tex]

We want to find grams of H, so we choose the one with grams of H on top.

[tex]\text{Mass of H} = \text{2.5 g NH}_{3} \times \dfrac{\text{3.024 g H}}{\text{17.03 g NH}_{3}} = \textbf{0.44 g H}\\\\\text{The mass of H is $\large \boxed{\textbf{0.44 g}}$}[/tex]

Answer:

D working alone

Explanation:

Working alone is the only option that could potentially be a safety hazard; if you have no one watching your back, errors could occur, like dropping glass or burning your hand, and no one is around to help you.

Choices A, B, and C are not correct because those are all good safety standards.

Answer:

Heat energy (Q) = 1.9925 KJ = 2 KJ (Approx)

Explanation:

Given:

Mass of copper (M) = 45 gram

Change in temperature (ΔT) = 71°C - 12°C = 59°C

Specific heat (c) =0.75 j /g*c

Find:

Heat energy (Q) = ?

Computation:

Heat energy (Q) = Mass(M) × Change in temperature (ΔT) × Specific heat (c)

Heat energy (Q) = 45 gram × 59°C × 0.75 j /g*c

Heat energy (Q) = 1991.25 J

Heat energy (Q) = 1.9925 KJ = 2 KJ (Approx)

Answer:

Explanation:

Soap breaks up the oil into smaller drops, which can mix with the water. It works because soap is made up of molecules with two very different ends. One end of soap molecules love water - they are hydrophilic. The other end of soap molecues hate water - they are hydrophobic.

Answer:

C. Its polar end mixes with the water so it can be washed away.

Explanation:

Just took test

Answer: Volume =  50.0 mL in liters : 50.0 / 1000 = 0.05 L

n = M x V

n = 0.20 x 0.05

n = 0.01 moles of solute

Explanation:

The number of moles of solute are present in 50.0 mL of 0.20 M of KNO₃ solution is 0.01 moles.

Moles will be calculated by using the molarity formula because molarity is define as the no. of moles of solute present in per liter of the solution as:

M = n/V, where

M = molarity of KNO₃ = 0.2 M

V = volume of solution = 50mL = 0.05L

Moles will be calculated as:

n = (0.2)(0.05) = 0.01 moles

Hence required moles are 0.01 moles.

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Answer:

The answer is NaOH

Explanation:

Strong bases are characterized by the fact that they dissociate completely in an aqueous solution. In this case, sodium hydroxide, NaOH, is classified as a strong base because it dissociates completely in an aqueous solution to form sodium cations, Na+, and hydroxide anions, OH−. Also, it is strong because it totally breaks in its ion. And the base which breaks totally in its atom called the strong base and which doesn't it that is a weak base.

Answer:

NaOH

Explanation:

Got it right in the test. Please mark as brainliest

Answer:

True statements: B and C

Explanation:

A is not true NaCl is product

D is not true the reaction occurs

Answer:

natural selection

Explanation:

it is a biological selection of genes, whether dominant or negative.

Answer:98g/mol

Explanation:

Answer:it is D

Explanation: it is only one that makes sense