Put the steps of the scientific method into the correct order.

What do we call atoms of the same elements with different mass numbers?

kakasveta [241]

Atoms of the same element with different mass numbers are called isotopes

6 0

2 years ago

Take it before its gone

MaRussiya [10]

Hello my friend thank you

8 0

2 years ago

A chemical equation is shown below. KNO3 → KNO2 + O2 What are the coefficients that should be added to balance this equation? Us

uysha [10]

20) Balanced chemical equation: 2KNO₃ → 2KNO₂ + O₂.

Potassium nitrate is decomposed on potassium nitrite and oxygen.

According to principle of mass conservation, number of atoms must be equal on both side of chemical reaction.

There are two potassium atoms, two nitrogen atoms and six oxygen atoms on both side of balanced chemical reaction.

Decomposition is reaction where one substance (in this example potassium nitrate) is broken down into two or more simpler substances (potassium nitrite and oxygen).

21) The answer is:

Balanced chemical reaction: double recplacement reaction.

MgCl₂(aq) + Na₂CO₃(aq) → MgCO₃(s) + 2NaCl(aq).

The magnesium (Mg) and the sodium (Na) replace each other making this a double replacement reaction.

Reactivity series is an empirical progression of a series of metals, arranged by their reactivity from highest to lowest (alkaline metals have highest reactivity and Noble metals lowest reactivity):

K > Ba > Sr > Na > Ca > Mg > Be > Al > Mn > Zn > Cr> Fe > Cd > Co > Ni > Sn > Pb > H(in acids) > Cu > Hg > Ag.

Metal higher in the reactivity series will displace another and it will be oxidized.

Magnesium is higher it this series than aluminium and aluminium is higher than copper.

22) The answer is: half life is 22 years.

Half-life is the time required for a quantity (in this example mass of the element) to reduce to half its initial value and is independent of initial concentration.

Mass of the element is reduced by half in 22 years from 45 grams to 22.5 grams.

First calculate the radioactive decay rate constant λ:

λ = 0.693 ÷ t.

λ = 0.693 ÷ 22 y.

λ = 0.0315 1/y.

ln(m/m₀) = -λ·t₁.

ln(4.8125/308) = -0.0315 1/y · t₁.

t₁ = 132.02 y.

7 0

2 years ago

"Compounds A and B react to give a single product, C. Write the rate law for each of the following cases and determine the units

olasank [31]

Answer:

Part a: Units of k is $M^{-2}s^{-1}$ where reaction is first order in A and second order in B

Part b: Units of k is $M^{-1}s^{-1}$ where reaction is first order in A and second order overall.

Part c: Units of k is $M^{-1}s^{-1}$ where reaction is independent of the concentration of A and second order overall.

Part d: Units of k is $M^{-3}s^{-1}$ where reaction reaction is second order in both A and B.

Explanation:

As the reaction is given as

$A+B \rightarrow C$

where as the rate is given as

$r=k[A]^x[B]^y$

where x is the order wrt A and y is the order wrt B.

Part a:

x=1 and y=2 now the reaction rate equation is given as

$r=k[A]^1[B]^2$

Now the units are given as

$r=k[A]^1[B]^2\\M/s =k[M]^1[M]^2\\M/s =k[M]^{1+2}\\M/s =k[M]^{3}\\M^{1-3}/s =k\\M^{-2}s^{-1} =k$

The units of k is $M^{-2}s^{-1}$

Part b:

x=1 and o=2

x+y=o

1+y=2

y=2-1

y=1

Now the reaction rate equation is given as

$r=k[A]^1[B]^1$

Now the units are given as

$r=k[A]^1[B]^1\\M/s =k[M]^1[M]^1\\M/s =k[M]^{1+1}\\M/s =k[M]^{2}\\M^{1-2}/s =k\\M^{-1}s^{-1} =k$

The units of k is $M^{-1}s^{-1}$

Part c:

x=0 and o=2

x+y=o

0+y=2

y=2

Now the reaction rate equation is given as

$r=k[A]^0[B]^2$

Now the units are given as

$r=k[B]^2\\M/s =k[M]^2\\M/s =k[M]^{2}\\M^{1-2}/s =k\\M^{-1}s^{-1} =k$

The units of k is $M^{-1}s^{-1}$

Part d:

x=2 and y=2

Now the reaction rate equation is given as

$r=k[A]^2[B]^2$

Now the units are given as

$r=k[A]^2[B]^2\\M/s =k[M]^2[M]^2\\M/s =k[M]^{2+2}\\M/s =k[M]^{4}\\M^{1-4}/s =k\\M^{-3}s^{-1} =k$

The units of k is $M^{-3}s^{-1}$

7 0

2 years ago

The volume of 0.05 M H2SO4 is needed to completely neutralise 15ml of 0.1 M NaOH solution is

Feliz [49]

V(NaOH)=15 mL =0.015 L
C(NaOH)=0.1 mol/L
C(H₂SO₄)=0.05 mol/L

2NaOH + H₂SO₄ = Na₂SO₄ + 2H₂O

n(NaOH)=V(NaOH)C(NaOH)=2n(H₂SO₄)
n(H₂SO₄)=V(H₂SO₄)C(H₂SO₄)

V(NaOH)C(NaOH)=2V(H₂SO₄)C(H₂SO₄)

V(H₂SO₄)=V(NaOH)C(NaOH)/{2C(H₂SO₄)}

V(H₂SO₄)=0.015*0.1/{2*0.05}=0.015 L = 15 mL

5 0

2 years ago