Ask & Answer: India's Largest Education Community

13.10 Half life of ${}_{38}{}^{90}Sr$ , $T_{1/2}$ = 28 years = 28 $*365*24*60*60$ secs = 0.883 $*{10}^9$ s

Mass of the isotope, m = 15 mg = 15 $*{10}^{-3}$ gms

90 g of ${}_{38}{}^{90}Sr$ contains 6.023 $*{10}^{23}$ atoms

No. of atoms in 15 mg of ${}_{38}{}^{90}Sr$ contains = $\frac{6.023*{10}^{23}}{90}*$ 15 $*{10}^{-3}$ = 1.0038 $*{10}^{20}$

Rate of disintegration $\frac{dN}{dt}$ = $?N$ , where $?$ = $\frac{0.693}{T_{1/2}}$ = $\frac{0.693}{0.883*{10}^9}$ /s = 7.848 $*{10}^{-10}$ $s^{-1}$

$\frac{dN}{dt}$ = 7.848 $*{10}^{-10}*$ 1.0038 $*{10}^{20}$ = 7.878 $*{10}^{10}$ atoms / second.

Yes, applications are open at Alliance School of Computer Science and Engineering for various courses. The mode of application is online. Aspirants need to apply at the official website for admission to the various programme. Candidates can fill out the application form on the institute's official website.

13.9 The strength of the radioactive source is given as:

$\frac{dN}{dt}$ = 8.0 mCi = 8 $\times {10}^{-3}$ $\times 3.7\times {10}^{10}$ decay/s = 296 $\times {10}^6$ decay/s, where

N = Required number of atoms

Given, half life of ${}_{27}{}^{60}Co$ , $T_{1/2}$ = 5.3 years = 5.3 $\times 365\times 24\times 60\times 60$ secs = 167 $\times {10}^6$ s

For decay constant $\lambda$ , we have rate of decay as:

$\frac{dN}{dt}$ = $\lambda N$ or

N = $\frac{1}{\lambda }\frac{dN}{dt}$ , where $\lambda$ = $\frac{0.693}{T_{1/2}}$ = $\frac{0.693}{167\mathrm{}\times {10}^6}$ /s = 4.1497 $\times {10}^{-9}$ $s^{-1}$

N = $\frac{296\mathrm{}\times {10}^6\mathrm{}}{4.1497\times {10}^{-9}}$ = 7.133 $\times {10}^{16}$ atoms

For ${}_{27}{}^{60}Co$ , mass of 6.023 $\times {10}^{23}$ atoms = 60 gms

Therefore, the mass of 7.133 $\times {10}^{16}$ atoms = $\frac{60}{6.023\times {10}^{23}}\times$ 7.133 $\times {10}^{16}$ gms = 7.106 $\times {10}^{-6}$ g

Mohammad Ali Jauhar University specifies the minimum qualification and aggregate required to apply for a course. Aspirants fulfilling the eligibility requirements can apply for admission. Below is the eligibility requirement for popular courses:

In order to get admission at Alliance School of Computer Science and Engineering, candidates must keep certain documents ready. Student can check the list of documents below:

• Scanned Class 10, Class 12 and graduation marksheet
• Leaving Certificate
• Aadhaar Card
• Passport-size photograph
• Signature

Note: The list of documents mentioned above are the general documents. For more details visit the official website.

(i) Ionization enthalpy. Because of high nuclear charge the ionization enthalpy of alkaline earth metals are higher than those of the corresponding alkali metals.

(ii) Basicity of oxides. Basicity of oxides of alkali metals are higher than that of alkaline earth metals.

(iii) Solubility of hydroxides of alkali metals is higher than that of alkaline earth metals. Alkali metals due to lower ionization enthalpy are more electropositive than the corresponding group 2 elements.

To be eligible for the BTech programme at Mohamed Sathak A J College of Engineering, students must have passed Class 12 with Physics, Chemistry, and Mathematics, securing at least 45% (40% for reserved categories). Lateral entry is available for Diploma and BSc holders with core Mathematics as one of the subjects. Admission is through Tamil Nadu Engineering Admissions (TNEA) 2025.

Yes, From the available informations, the Civil Engineering department at SRM Easwari Engineering College conducts regular workshops. The college conducts "lots of workshops". Additionally, the college's website outlines the department's commitment to student development, including effective communication and problem-solving skills, which are often enhanced through workshop activities. For Getting More details about Workshops done by this college you must contact that college office. also I prefer you can contact a senior student for more informations regarding workshop. 

It is because ionization enthalpy? H_i of potassium = 419 kJ mol^-1. Ionization enthalpy of sodium = 496 KJ mol^-1. Since Ionization enthalpy of potassium is less than that of sodium, potassium is more reactive than sodium.

Let x be the oxidation state of Na in Na₂O₂     

Then, 2x + 2 (-1) = 0  

=>2x – 2 = 0  

=> x =  +1.

Yes, the Dr. Shakuntala Misra National Rehabilitation University does have a seat reservation policy for all of its programmes, including BA. The university keeps a minimum of 50% of seats available in all academic programmes for disabled students, out of which 25% of total seats are reserved for visually impaired students. Such seat reservations help every students get an equal chance to secure a seat in their preferred course.

All the alkali metals have one valence electron, ns1 outside the noble gas core. The loosely held s-electron in the outermost valence shell of these elements makes them the mostelectropositive metals, i.e. they readily lose electron to give monovalent M+ ions. Hence, they are never found in free state in nature.

13.3 Atomic mass of ${}_7{}^{14}N$ nitrogen , m = 14.00307 u

A nucleus of ${}_7{}^{14}N$ nitrogen contains 7 protons and 7 neutrons.

Hence, the mass defect of this nucleus, Δm = 7 $m_p$ + 7 $m_n$ - m, where

Mass of a proton, $m_p$ = 1.007825 u

Mass of a neutron, $m_n$ = 1.008665 u

Therefore, Δm = 7 $\times$ 1.007825+ 7 $\times$ 1.008665 – 14.00307 = 0.11236 u

But 1 u = 931.5 MeV/ $c^2$

Δm = 104.66334 MeV/ $c^2$

The binding energy of the nucleus, $E_b$ = Δm $c^2$ , where c = speed of light

$E_b=$ (104.66334/ $c^2$ ) $\times$ $c^2$ = 104.66334 MeV

The general characteristics and gradation in properties of alkaline earth metals are:

• Atomic size goes on increasing down the group.
• Ionisation energy goes on decreasing down the group.
• They are harder than alkali metals.
• They are less electropositive than alkali metals.

Electropositive character increases on going down the group.